That way, browsers will suggest to the users to upload an image file instead of any kind of file.
The behaviour is in-line with Element's, which specifies the same attribute when selecting an avatar.
Please note that it does not prevent users from uploading non-image files as avatars, as browsers interpret that attribute as a mere suggestion, which can be bypassed in the file select dialog.
Partially fixes#982.
* Remove comments
* Show custom emoji first in suggestions
* Show global image packs in emoji picker
* Display emoji and sticker in room settings
* Fix some pack not visible in emojiboard
* WIP
* Add/delete/rename images to exisitng packs
* Change pack avatar, name & attribution
* Add checkbox to make pack global
* Bug fix
* Create or delete pack
* Add personal emoji in settings
* Show global pack selector in settings
* Show space emoji in emojiboard
* Send custom emoji reaction as mxc
* Render stickers as stickers
* Fix sticker jump bug
* Fix reaction width
* Fix stretched custom emoji
* Fix sending space emoji in message
* Remove unnessesary comments
* Send user pills
* Fix pill generating regex
* Add support for sending stickers
