Add a CONTRIBUTING.md file as guidance for contributors

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
2 jobs for gitlab-ci-alt in 1 minute and 7 seconds (queued for 2 seconds)
latest
Status Name Job ID Coverage
  Test
passed pages #814392582

00:01:07

 
  Deploy
passed pages:deploy

00:00:07