15.10 Adds a color for the line between the toolbar buttons

Contributes to: issue CURA-60

resources/themes/cura/theme.json

@@ -70,6 +70,7 @@
         "button_hover": [140, 144, 154, 255],
         "button_active": [12, 169, 227, 255],
         "button_active_hover": [34, 150, 199, 255],
+        "button_lining": [140, 144, 154, 255],
         "button_text": [255, 255, 255, 255],
         "button_disabled": [245, 245, 245, 255],
         "button_tooltip_text": [35, 35, 35, 255],