Adds esnext to jshint rc for Map Set usage that needs es6
Adds esnext to jshint rc for Map Set usage that needs es6

hishamabdelrahman/osgjs,jmirabel/osgjs,jtorresfabra/osgjs,jtorresfabra/osgjs,gideonmay/osgjs,gideonmay/osgjs,jtorresfabra/osgjs,jmirabel/osgjs,gideonmay/osgjs,cedricpinson/osgjs,cedricpinson/osgjs,kkuunnddaannkk/osgjs,hishamabdelrahman/osgjs,hishamabdelrahman/osgjs,kkuunnddaannkk/osgjs,jmirabel/osgjs,kkuunnddaannkk/osgjs,cedricpinson/osgjs