- The translation key needs the .qm files to be included to work (so it's useless right now; the CMake
script needs to be adjusted to install those files and make this key work properly)
- The Purism custom keys don't seem to be relevant anymore (so that's another useless thing)
- The donation key needs an URL to be useful (the FIXME is still left so it can be readded later)

Co-authored-by: DeepBlueV7.X <nicolas.werner@hotmail.de>

Some of our build files and resource files are licensed as that, but not
our actual code. This leads to funny issues, that GNOME software
considers Nheko proprietary. To work around that, just put GPL there.

Fixes https://github.com/flathub/io.github.NhekoReborn.Nheko/issues/1

- Update version numbers and documentation
- Fix github releases oauth key