Add a simple contributing file.
Add a simple contributing file.

Mostly, this is a set of links to other, existing documentation.  However,
the GitHub web UI will recommend developers review this file before
submitting a pull-request.  It's a simple nudge to "do the right thing".

root-mirror/root,karies/root,olifre/root,olifre/root,karies/root,root-mirror/root,olifre/root,olifre/root,zzxuanyuan/root,karies/root,zzxuanyuan/root,root-mirror/root,olifre/root,olifre/root,root-mirror/root,root-mirror/root,zzxuanyuan/root,karies/root,karies/root,zzxuanyuan/root,zzxuanyuan/root,zzxuanyuan/root,karies/root,olifre/root,olifre/root,karies/root,root-mirror/root,karies/root,root-mirror/root,zzxuanyuan/root,zzxuanyuan/root,zzxuanyuan/root,karies/root,zzxuanyuan/root,olifre/root,zzxuanyuan/root,olifre/root,zzxuanyuan/root,olifre/root,karies/root,root-mirror/root,root-mirror/root,root-mirror/root,root-mirror/root,karies/root