chore: update robots.txt to allow api/app-store (#8023)

apps/web/public/robots.txt

@@ -4,4 +4,6 @@ Disallow: /api
 Disallow: /static/locales
 
 # Specifically allow access to OG Image api, otherwise eg Twitter won't render these images.
-Allow: /api/social/og/image
+Allow: /api/social/og/image
+# Specifically allow access to api/app-store to allow search engines to fetch assets
+Allow: /api/app-store/