add 0.21.2 debs to deb.leap.se

After some time, there's again a working package under debian/

I'm creating this issue to track "official" builds - I can also get a ppa running in the meantime to offer a more sane alternative to fat snaps to debian/ubuntu users.

At this point, I don't see why not try to include a more polished version in debian itself (other than me fixing all the lintian errors). I really hope not to change once again the client codebase in some time.