Support of Budgie on FreeBSD

[OlivierDuchateau]

The Budgie desktop is now available on FreeBSD. I wonder, if you think is useful to add instructions how to install on this system.

I maintain this documentation on my own repository, but I would like something more official.

[JoshStrobl]

Hey @OlivierDuchateau, a PR would be welcome to https://github.com/BuddiesOfBudgie/docs

We have a Getting Budgie page on our new documentation center and I think FreeBSD instructions would be great there! Would also need to change "are available across a wide variety of Linux-based operating systems." at the top of it to something like "are available across a wide variety of operating systems." so it's not "Linux-based" anymore :)

The GitHub wiki will be nuked once everything has been ported over.