Rework Emoji Implementation

Use emoji data from a generated dict based on the offical unicode docs, this makes it easier to update in the future
Rewrite the emoji chooser
Add a search field to the emoji chooser
The emoji chooser is loaded async
Update to current Unicode 11 Noto theme
Add twemoji theme
Move the atlas generator code into a new project

Le téléchargement c'est par la :
https://gajim.org/downloads/?C=M;O=D