Add app to the official AppImage catalog + Making AppImages updatable (make .zsync)

[avczar]

Because it would be a shame not to give your app the visibility it deserves! 🌞
➡️ Add the app to the official AppImage catalog by following these instructions: https://github.com/AppImage/appimage.github.io#how-to-submit-appimages-to-the-catalog

And, because this is a good thing for full support of Gear Lever (and all others AppImage compatible managers). 😎
➡️ Making the app widely updatable: https://docs.appimage.org/packaging-guide/optional/updates.html
More info about updates support by Gear Lever: https://mijorus.it/posts/gearlever/update-url-info/
Operational example: Helium Browser has this.