Accept more file extensions for emojis (jpg, webp...)

Currently, there’s a client-side authorized extensions via accept=".png,.gif".

Editing accept=".png,.gif" in our browser allows uploads of other formats, including animated webp, which is nice since there support alpha transparency.

The authorized emojis extension can’t circumvent the authorized uploads extensions from the site settings (jpg, jpeg, png, gif, heic, heif, webp by default).

My suggestion is to expand the authorized formats in the emoji selector.

Would a PR be accepted?