We now have an OpenSBI mailing list available for development
and discussiong so update contributing.md accordingly. The
Github PR based review and issue tracking will also continue
to exist.
Signed-off-by: Anup Patel <anup.patel@wdc.com>
Explicitely mention that this project adheres to the Developer
Certificate of Origin (DCO) and include this short text.
Also reformat the file to have lines bounded at 80 chars and add some
more details regarding the expected commit message format.
Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
