Linux: Embed AppImage update information

[shuvashish76]

Request to provide .zsync file for AppImage delta updates.
Updating will take less amount of data and time due to downloading only diff.

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

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

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

[SimonSchubert]

Implemented in f50b25a.

What shipped

• AppImage builds now embed GitHub Releases update info (gh-releases-zsync|…|latest|LinuxCommandLibrary-*-linux.AppImage.zsync).
• CI generates and uploads a matching .zsync next to the AppImage on each release.
• AppImages are built with the final versioned name so the zsync Filename header matches the release asset.

How to use (from the next v* release onward)

Tools such as AppImageUpdate, AppImageLauncher, AM/AppMan can delta-update using the embedded metadata and the published .zsync file.

Older AppImages without update info still need a one-time full redownload, then subsequent updates can use zsync.