officejs_support_request_ui: support Ctrl+S in discussion view editor

form_discussion_view embeds an editor, but it did not expose notifySubmit
method to child gadgets. Because using Ctrl+S in the editor calls
notifySubmit on parent gadget, Ctrl+S was causing a page crash.

Expose such a method that would submit a comment when called.
4 jobs for <span class="ref-name">fix/officejs-support-ctrl-s</span> in 0 seconds
Status Job ID Name Coverage
  External
passed ERP5.CodingStyleTest-TestRunner2

09:54:58

failed ERP5.UnitTest-TestRunner2

10:55:03

passed ERP5.CodingStyleTest-TestRunner2

00:43:58

failed ERP5.UnitTest-TestRunner2

01:30:24