Embed AppImage update information

[shuvashish76]

Is your feature request related to a problem? Please describe.

When trying to update via AppImageUpdate

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

Request to embed update the information as mentioned there so that users can update them directly.

This is a common standard for updating AppImages.
AppImage having update information would also recognized by other software e.g. AppImageLauncher

Lots of projects already support updating AppImage e.g: LibreWolf, KeePassXC, Sigil etc.