Add Code of Conduct (#1961)
Add Code of Conduct (#1961)

Adopt the Contributor Covenant CoC for the community forum, include a pointer from CODE_OF_CONDUCT.md in the Boulder repo. 

benileo/boulder,ibukanov/boulder,ZCloud-Firstserver/boulder,lucasallan/boulder,jfrazelle/boulder,ZCloud-Firstserver/boulder,letsencrypt/boulder,jsha/boulder,sophie-h/boulder,jsha/boulder,letsencrypt/boulder,jfrazelle/boulder,jcjones/boulder,jcjones/boulder,lucasallan/boulder,bmw/boulder,ibukanov/boulder,ZCloud-Firstserver/boulder,ZCloud-Firstserver/boulder,bmw/boulder,jcjones/boulder,benileo/boulder,letsencrypt/boulder,lucasallan/boulder,ibukanov/boulder,sophie-h/boulder,bmw/boulder,sophie-h/boulder,jfrazelle/boulder,jsha/boulder,benileo/boulder,jfrazelle/boulder,jcjones/boulder,benileo/boulder