Issue #2865971 by alexpott, droplet, xjm, martin107, joelpittet, Cottser, idebr, Mile23: Use stylelint as opposed to csslint in core
Issue #2815077 by drpal, mradcliffe, effulgentsia, mpdonadio, nod_, droplet, alexpott, nedjo, tizzo, David_Rothstein, pfrenssen: Adopt airbnb javascript style guide v13 as new baseline javascript coding standards for Drupal 8 core and contrib