[javascript-hint addon] Add ECMAScript 2015 keywords
[javascript-hint addon] Add ECMAScript 2015 keywords

This explicitly adds keywords that are already syntax-highlighted
and correctly parsed by CodeMirror already in the JavaScript mode.

hackmdio/CodeMirror,codio/CodeMirror,dperetti/CodeMirror,notepadqq/CodeMirror,SidPresse/CodeMirror,pabloferz/CodeMirror,notepadqq/CodeMirror,nightwing/CodeMirror,jkaplon/CodeMirror,jkaplon/CodeMirror,wingify/CodeMirror,thomasjm/CodeMirror,SidPresse/CodeMirror,jkaplon/CodeMirror,mtaran-google/CodeMirror,hackmdio/CodeMirror,wingify/CodeMirror,pabloferz/CodeMirror,thomasjm/CodeMirror,codio/CodeMirror,codio/CodeMirror,SidPresse/CodeMirror,notepadqq/CodeMirror,nightwing/CodeMirror,namin/CodeMirror,mtaran-google/CodeMirror,thomasjm/CodeMirror,namin/CodeMirror,hackmdio/CodeMirror,dperetti/CodeMirror,wingify/CodeMirror,mtaran-google/CodeMirror,namin/CodeMirror,pabloferz/CodeMirror,nightwing/CodeMirror,dperetti/CodeMirror