[Feature] Integrity checking for the AppImages

[iTrooz]

Pre-submit checks

• I checked for similar issues beforehand, but could not find any. I could not add my proposal to any existing issue.
• I am going to take the time to to fill in all the required details. I know that the bug report will be dismissed otherwise.

Feature description

[copied from the original issue]
AppImages are files which can get really big in size, and download errors can occur with such sizes
I propose to add some way to (at least try to) verify it's integrity

Proposed solution

Add a checksum (CRC ?) in the AppImage Spec and verify it on integration/on launch

Note : other applications might try to directly move AppImages in the ~/Applications folders (or whatever is defined) so checking the integrity on integration might not be enough. Maybe at first launch ?

Alternative solutions you considered

No response

Additional context

Originally started on
AppImage/AppImageSpec#35

[iTrooz]

OOPS
I just realized that this is the wrong repository, so sorry for the confusion