Hi,

This patch updates Zrythm. I explicitly enabled rtmidi support (it was
implicitly enabled before), and also removed the xdg-open patch as it's
no longer necessary (the full path to xdg-open is now stored during
configuration).

Also, the versioning scheme changed to follow SemVer 2.0 (see
PACKAGING.md for details). I don't think there should be any problems
upgrading since the previous versions started with 0.

Thanks,
Alex