[javascript mode] Allow default values on array pattern elements
[javascript mode] Allow default values on array pattern elements

Closes #5556

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