[simple-mode addon] Don't drop regexp unicode flags
[simple-mode addon] Don't drop regexp unicode flags

See https://discuss.codemirror.net/t/some-of-my-simple-mode-unicode-patterns-dont-work-why/3101

dperetti/CodeMirror,hackmdio/CodeMirror,dperetti/CodeMirror,wingify/CodeMirror,pabloferz/CodeMirror,pabloferz/CodeMirror,nightwing/CodeMirror,dperetti/CodeMirror,pabloferz/CodeMirror,nightwing/CodeMirror,hackmdio/CodeMirror,wingify/CodeMirror,hackmdio/CodeMirror,wingify/CodeMirror,nightwing/CodeMirror