Mention solidus in CONTRIBUTING.md
Mention solidus in CONTRIBUTING.md

ckk-scratch/solidus,devilcoders/solidus,scottcrawford03/solidus,lsirivong/solidus,forkata/solidus,xuewenfei/solidus,bonobos/solidus,ckk-scratch/solidus,pervino/solidus,lsirivong/solidus,ckk-scratch/solidus,scottcrawford03/solidus,xuewenfei/solidus,pervino/solidus,Senjai/solidus,Arpsara/solidus,grzlus/solidus,richardnuno/solidus,xuewenfei/solidus,Senjai/solidus,athal7/solidus,richardnuno/solidus,forkata/solidus,jsurdilla/solidus,grzlus/solidus,athal7/solidus,bonobos/solidus,devilcoders/solidus,bonobos/solidus,Senjai/solidus,richardnuno/solidus,jordan-brough/solidus,jordan-brough/solidus,athal7/solidus,richardnuno/solidus,jordan-brough/solidus,lsirivong/solidus,jordan-brough/solidus,scottcrawford03/solidus,pervino/solidus,forkata/solidus,devilcoders/solidus,Arpsara/solidus,jsurdilla/solidus,athal7/solidus,grzlus/solidus,lsirivong/solidus,scottcrawford03/solidus,forkata/solidus,Arpsara/solidus,bonobos/solidus,ckk-scratch/solidus,jsurdilla/solidus,xuewenfei/solidus,jsurdilla/solidus,Senjai/solidus,Arpsara/solidus,pervino/solidus,grzlus/solidus,devilcoders/solidus