Fix double border on custom feed posts (web)

Add missing visibility check for ageAssuranceBanner on non-discover
feeds. The banner was being added to the feedItems array without
checking ageAssuranceBannerState.visible, causing the first post's
rowIndex to be 1 instead of 0, which prevented hideTopBorder from
being set correctly. This was particularly visible on web when
directly navigating to a custom feed URL.

modules/expo-bluesky-gif-view/src/GifView.types.js

@@ -0,0 +1 @@
+export {};