Add Qubes Community links to Qubes OS documentation

[deeplow]

Good catch @whoami! Some other discussion on this happenning on this thread:

Ready to launch

We’re almost ready to lauch the forum! (we just need consensus on this). Some other stuff can also be tweaked later on, but it is non-blocking for the launch. This is a wiki post, meaning that other users can edit it. Where to announce? on qubes-users - done on the website - done on /r/Qubes - done on unofficial chat channels - unnoficial, feel free to do it there Other things to do after launch add to qubes-os.org/support/ add on website’s footer add mentions in the documentation t…

@adw