chore: update changelog

[SimJoSt]

Hey, I've noticed that the changelog (https://github.com/e-alfred/flowupload/blob/master/CHANGELOG.md) hasn't been up-to-date with the newest releases (https://github.com/e-alfred/flowupload/releases) for some time now.
It would be great to have it updated, as it is our first references while updating the app, to see what changed. If you don't intend to use it anymore, I recommend removing it completely and only rely on GitHubs releases feature.

Thanks for the great work 👍