Several fixes and additions

[ghost]

• I've being using megasync for a while without any issues, so it's good to go (plus their dependencies)
• Fixed the issue with keepassxc not being able to connect on firefox
• Fixed the openmsx-catapult not installing the proper .desktop item
• Moved webkitgtk from testing, as is a direct dep of lutris
• Moved rclone from testing, I've being using it daily since and it works as expected
• Added: Fuse Emulator: a ZX-Spectrum emulator
• Added: Geeqie: A simple imageviewer, fork of gqview

[MalteKiefer]

Please split the PR. Make a separate PR for each package.