GFK Q2 pre-launch tweaks (#4921)

* Adding `installing_and_managing_fonts` to module contents

* Alt text for illos in `installing_and_managing_fonts`

* Alt text for illos in the new Glossary terms

* Typo correction + link inseraion for `installing_and_managing_fonts`

* Links in Counter entry

* Typos in Icon Font entry

* Typos + minor tweaks to Legibility entry

* Copy tweak to Readability entry

* Adding axis shorthand to Parametric Font entry

* Links in `using_type_in_ar_and_vr`

* Related terms  in `using_type_in_ar_and_vr`

* Copy tweaks to `using_type_in_ar_and_vr`

* Better related terms for `using_type_in_ar_and_vr`

* Adding links to `type_selection_for_ar_vr`

* Mass-fixing malformed links to Glossary entries

* Correcting inter-module URL format

* Various URLs, formatting tweaks, typos, etc. in `type_selection_for_ar_vr`

* Glossary URLs in `spatial_classification_of_typography_in_ar_vr`

* Glossary links in `designing_for_ar_vr`

* Glossary links in `using_type_in_ar_and_vr`

* Alt text for all illos in `designing_for_ar_vr`

* Alt text for all illos in `introducing_ar_vr`

* Alt text for all illos `spatial [...]`

* Alt text for all illos in`technical challenges [...]`

* Alt text for all illos in `type_selection [...]`

* Excerpts for AR/VR lessons + `installing...` lesson

* Excerpts for all “History of type” articles

* Excerpts for all new Glossary terms

* Alt text for all illos in “Fitting the line”

* Alt text for all illos in “The tight not touching style”

* Removing missing URL

* Fixes + tweaks to copy in “Introducing AR/VR”

* Fixes + tweaks to copy in “Designing for AR/VR”

* Fixes + tweaks to copy in “Type selection for AR/VR”

* Fixes + tweaks to copy in “Spatial classification of typography in AR/VR”

* Fixes + tweaks to copy in “Technical challenges for typography in AR/VR”

* “Further reading” > “Useful links”

* Fixes + tweaks to copy in “Installing & managing...”

* Extra topics for AR/VR

* Removing “Advancing type” module + references

* Fixing bg color on “Material symbols” `thumbnail.svg`

* 3 × actual `thumbnail.svg` illos for “History of type”

* New (and optimized) AR/VR illo exports

* Correcting AR/VR illos’ file extensions for new files

* Updating figcaption in “Introducing AR/VR” article

cc-by-sa/knowledge/glossary/terms/counter/content.md

@@ -1,9 +1,9 @@
-A counter, or counterform, is the transparent (negative or white) space enclosed inside a letterform. Counters can be closed, as in “o” and “d”, or open, as in “c” and “u.”
+A counter, or counterform, is the transparent (negative or white) space enclosed inside a [letterform](/glossary/letterform). Counters can be closed, as in “o” and “d”, or open, as in “c” and “u.”
 
 <figure>
 
-![INSERT_ALT](images/thumbnail.svg)
+![The lowercase letters “odcu” with their counter highlighted.](images/thumbnail.svg)
 
 </figure>
 
-The name comes from the craft of traditional font production, in which a counterpunch makes indentations in the metal punch that is used for creating letter moulds. For more about this process, see the [Punchcutting](https://en.wikipedia.org/wiki/Punchcutting) entry on Wikipedia.
+The name comes from the craft of traditional font production, in which a counterpunch makes indentations in the metal punch that is used for creating letter moulds. For more about this process, see [the “Punchcutting” entry on Wikipedia](https://en.wikipedia.org/wiki/Punchcutting).

cc-by-sa/knowledge/glossary/terms/counter/term.textproto

@@ -1,3 +1,3 @@
 name: "Counter"
-excerpt: "EXCERPT_TBC"
+excerpt: "The transparent space enclosed inside a letterform. Counters can be closed, as in “o” and “d”, or open, as in “c” and “u.”"
 related_lessons: "an_overview_of_latin_type_anatomy"

cc-by-sa/knowledge/glossary/terms/icon_font/content.md

@@ -2,7 +2,7 @@ An icon [font](/glossary/font) is a font that exclusively contains icon [glyphs]
 
 <figure>
 
-![INSERT_ALT](images/thumbnail.svg)
+![A representation of font files, with the weight of the Material Symbols font matching the weight of the type shown on the Google Sans font files.](images/thumbnail.svg)
 
 </figure>
 
@@ -10,5 +10,5 @@ Using fonts to render icons has multiple benefits:
 
 - Being vector-based, they’re infinitely scalable, unlike rasterized images.
 - Contained in one file, the file size is considerably smaller than a collection of individual images—even vector-based ones.
-- When used on the web, they can be colored and positioned just using CSS, and browser support is excellent.
-- When using variable icon fonts , they’re customizable in a way that allows them to be more closely matched to any accompanying type.
+- When used on the web, they can be colored and positioned using just CSS, and browser support is excellent.
+- When using variable icon fonts, they’re customizable in a way that allows them to be more closely matched to any accompanying type.

cc-by-sa/knowledge/glossary/terms/icon_font/term.textproto

@@ -1,3 +1,3 @@
 name: "Icon font"
-excerpt: "EXCERPT_TBC"
+excerpt: "A font that exclusively contains icon glyphs rather than alphanumeric glyphs."
 related_lessons: "making_sense_of_typographic_classifications"

cc-by-sa/knowledge/glossary/terms/icon_symbol/content.md

@@ -2,7 +2,7 @@
 
 <figure>
 
-![INSERT_ALT](images/thumbnail.svg)
+![A collection of glyphs from Google’s Material Icons icon set.](images/thumbnail.svg)
 
 </figure>
 

cc-by-sa/knowledge/glossary/terms/icon_symbol/term.textproto

@@ -1,3 +1,3 @@
 name: "Icon & symbol"
-excerpt: "EXCERPT_TBC"
+excerpt: "An icon is a literal, visual representation of the thing it represents, whereas a symbol can be a more abstract representation of something."
 related_lessons: "making_sense_of_typographic_classifications"

cc-by-sa/knowledge/glossary/terms/legibility/content.md

@@ -1,12 +1,12 @@
-Legibility describes how a [typeface](/glossary/typeface)’s [glyphs](/glossary/glyph) can be correctly identified as [characters](/glossary/character) and words, including how individual characters can be distinguished from one another. Legibility should not be confused with [readability](/glossary/readability), although legibility does affect readability.
+Legibility describes how a [typeface](/glossary/typeface)’s [glyphs](/glossary/glyph) can be correctly identified as [characters](/glossary/character) and words, including how individual characters can be distinguished from one another. Legibility should not be confused with [readability](/glossary/readability), although legibility does *affect* readability.
 
 <figure>
 
-![INSERT_ALT](images/thumbnail.svg)
+![“1Il 0Oo” set in four different typefaces. Many of these characters in two typefaces on the left are indistinguishable, whereas the two examples on the right are far more legible.](images/thumbnail.svg)
 
 </figure>
 
-Some typefaces are inherently more legible than others, such as those with distinct shapes for “1,” capital “i,” and lowercase “l” (1Il); or “0”, capital “O,” and lowercase “o” (0Oo). Still, the typography of the [text](/glossary/text_copy) (for example, choices of foreground and background color, [font](/glossary/font) size, [weight](/glossary/weight), and [tracking](/glossary/tracking_letter_spacing)) will influence the legibility.
+Some typefaces are inherently more legible than others, such as those with distinct shapes for “1,” capital “I,” and lowercase “l” (1Il); or “0”, capital “O,” and lowercase “o” (0Oo). Still, the [typography](/glossary/typography) of the [text](/glossary/text_copy) (for example, choices of foreground and background color, [font](/glossary/font) size, [weight](/glossary/weight), and [tracking](/glossary/tracking_letter_spacing)) will influence the legibility.
 
 Legibility is a necessary prerequisite to readability; by affecting legibility, these factors also affect the readability of any [type](/glossary/type). A typeface rendered at a very small size will not be legible or readable. Increasing the font size will eventually make it legible, but it may not make it readable. For example, people may be able to read the text, but not comfortably—such as in a dense block of legal “small print.”
 

cc-by-sa/knowledge/glossary/terms/legibility/term.textproto

@@ -1,6 +1,6 @@
 alt_ids: "legibility_readability"
 name: "Legibility"
-excerpt: "EXCERPT_TBC"
+excerpt: "Describes how a typeface’s glyphs can be correctly identified as characters and words, including how individual characters can be distinguished from one another."
 related_lessons: "why_care_about_typography"
 related_lessons: "choosing_reliable_typefaces"
 related_lessons: "exploring_typefaces_with_multiple_weights_or_grades"

cc-by-sa/knowledge/glossary/terms/material_symbols/content.md

@@ -2,7 +2,7 @@ Google Fonts offers two collections as [icon fonts](/glossary/icon_font): [Mater
 
 <figure>
 
-![INSERT_ALT](images/thumbnail.svg)
+![On the left, four horizontal sliders to control the variable axes Weight, Fill, Grade, and Optical Size. On the right, a glyph from the Material Symbols font, affected by each control.](images/thumbnail.svg)
 
 </figure>