Linux: Embed AppImage update information

When trying to update via [AppImageUpdate](https://github.com/AppImageCommunity/AppImageUpdate)

AppImage having update information would also recognized by other software e.g. [AppImageLauncher](https://github.com/TheAssassin/AppImageLauncher) , [AppImageUpdate](https://github.com/AppImageCommunity/AppImageUpdate), [AppManager](https://github.com/kem-a/AppManager), [AM](https://github.com/ivan-hc/AM) etc...

info:
- https://github.com/AppImageCommunity/AppImageUpdate#update-information-overview
- https://github.com/AppImage/AppImageSpec/blob/master/draft.md#update-information
- https://github.com/ivan-hc/AppImage-tips#how-to-add-delta-updates

Lots of projects already support updating AppImage e.g: [LibreWolf](https://gitlab.com/librewolf-community/browser/appimage/-/releases), [KeePassXC](https://github.com/keepassxreboot/keepassxc/releases), [Sigil](https://github.com/Sigil-Ebook/Sigil/releases) etc.

AppImage delta updates which will take less amount of data and time due to downloading only `diff`.