Adding docs about adding new check files
Adding docs about adding new check files

jessamynsmith/fontbakery,googlefonts/fontbakery,graphicore/fontbakery,vitalyvolkov/fontbakery,moyogo/fontbakery,googlefonts/fontbakery,graphicore/fontbakery,moyogo/fontbakery,vitalyvolkov/fontbakery,googlefonts/fontbakery,davelab6/fontbakery,vitalyvolkov/fontbakery,moyogo/fontbakery,graphicore/fontbakery