Double-tap to edit a message on mobile not working

Double-tap to edit a message on mobile not working

Spawned from discussion here, https://gitlab.com/gitlab-org/gitter/webapp/issues/2225#note_196713043

I am not sure if this ever worked but it at least tried to open the textarea on mobile before, see https://gitlab.com/gitlab-org/gitter/webapp/issues/1113

Seems to work just fine on Android which uses the same webview chat area and is in our docs