Embed AppImage update information

[shuvashish76]

When trying to update via AppImageUpdate

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

info:

• https://github.com/AppImageCommunity/AppImageUpdate#update-information-overview
• https://github.com/AppImage/AppImageSpec/blob/master/draft.md#update-information

[edneyosf]

@shuvashish76 To update Edconv from AppImage, simply replace the file with the new version.

[shuvashish76]

simply replace the file with the new version.

That's not a good solution. With embedded update information i.e zsync method downloads necessary changes diff only so it'll take less time and less data to update.

[edneyosf]

@shuvashish76 I understand, could you help me with this? Open a PR or assist me, please?

[shuvashish76]

Please see this comment: warreth/OpenlibExtended#56 (comment)

[edneyosf]

If I have free time and want to do it, I will add it (if someone doesn't do it before me). Sorry, but it's not a priority right now.

[shuvashish76]

No issues, I understand.
guide specifically for this https://github.com/ivan-hc/AppImage-tips

[edneyosf]

@shuvashish76 thank you!