add contributing docs on making a plugin [skip ci] (#542)
add contributing docs on making a plugin [skip ci] (#542)

* add contributing docs on making a plugin [skip ci]

* fixes [skip ci]

guybedford/babel,vadzim/babel,claudiopro/babel,shuhei/babel,maurobringolf/babel,kellyselden/babel,babel/babylon,existentialism/babel,hulkish/babel,shuhei/babel,maurobringolf/babel,babel/babel,chicoxyzzy/babel,babel/babel,PolymerLabs/babel,samwgoldman/babel,vadzim/babel,PolymerLabs/babel,shuhei/babel,hulkish/babel,kaicataldo/babel,kaicataldo/babel,hulkish/babel,kellyselden/babel,guybedford/babel,jridgewell/babel,PolymerLabs/babel,Skillupco/babel,jridgewell/babel,Skillupco/babel,guybedford/babel,Skillupco/babel,existentialism/babel,jridgewell/babel,kellyselden/babel,kaicataldo/babel,claudiopro/babel,samwgoldman/babel,existentialism/babel,jridgewell/babel,claudiopro/babel,hzoo/babel,samwgoldman/babel,kellyselden/babel,hulkish/babel,hzoo/babel,babel/babel,Skillupco/babel,chicoxyzzy/babel,chicoxyzzy/babel,kaicataldo/babel,cbishopvelti/babylon,maurobringolf/babel,chicoxyzzy/babel,hzoo/babel,babel/babel,hzoo/babel