Add Mozilla Code of Conduct file
Add Mozilla Code of Conduct file

Fixes #401.

_(Message COC002)_
luser/sccache2,luser/sccache2,glandium/sccache,mozilla/sccache,glandium/sccache,luser/sccache2,mozilla/sccache,glandium/sccache,mozilla/sccache,luser/sccache2,glandium/sccache