Update freebsd.md

Merged username-removed-27490 requested to merge (removed):master into master

I checked the README and it worked. Some notes:

docker is not a BSD thing, so I change way of running the runner to shell, docker is problematic and unstable on BSDs. Links are up to date. gitlab-runner service is not supported on BSD:

agilob:~/ $ gitlab-ci-multi-runner-freebsd-386 service                                                                                                                                         [13:07:38]
FATAL: Command service not found. 

so it must be run with run method. I have two runners on now.