I couldn’t find it on GitHub and couldn’t see a way to submit a new app on the site.

Building static paths to serve files (gifs on this case) is not a good path for decentralization. It would be better to store the sha256 of the file on the note and then query the relays if they have that hash on their disks. This way you don't care which server the file is coming from, it might even be cached on the machine and notes will be future-proof like the rest of nostr.