Add "My collections" page (#37552)

app/javascript/mastodon/features/collections/utils.ts

@@ -0,0 +1,11 @@
+import {
+  isClientFeatureEnabled,
+  isServerFeatureEnabled,
+} from '@/mastodon/utils/environment';
+
+export function areCollectionsEnabled() {
+  return (
+    isClientFeatureEnabled('collections') &&
+    isServerFeatureEnabled('collections')
+  );
+}