fix(getting-started): Add `app` property to Vue 3 SDK init snippet (#67137)

A GH user [pointed
out](https://github.com/getsentry/sentry-javascript/issues/6629) that
our in-product getting started snippet for Vue 3 was missing for the
`app` property. This PR adds the missing property (See [Sentry
docs](https://docs.sentry.io/platforms/javascript/guides/vue/#configure))

static/app/gettingStartedDocs/javascript/vue.tsx

@@ -52,7 +52,8 @@ type Params = DocsParams<PlatformOptions>;
 
 const getSentryInitLayout = (params: Params, siblingOption: string): string => {
   return `Sentry.init({
-    ${siblingOption === VueVersion.VUE2 ? `Vue,` : ''}dsn: "${params.dsn}",
+    ${siblingOption === VueVersion.VUE2 ? 'Vue,' : 'app,'}
+    dsn: "${params.dsn}",
     integrations: [${
       params.isPerformanceSelected
         ? `