include the version number either in the `.desktop` file or the github release tag

[DetachHead]

i use AppManager to install my appimages and keep them up to date. i believe it uses two different methods to determine the version of an appimage:

• the X-AppImage-Version property in the .desktop file
• if that property doesn't exist, check the github release tag

the github release tag fallback seems to work well for most appimages, but not this one. since the release workflow seems to just always update the latest tag instead of creating a new release with each version, like this. github already supports using /latest to fetch the latest release anyway, so that functionality would not be lost.

another benefit of creating separate releases is that it's easier for users to downgrade to old versions if they want.