Allow comments to be added to feedback without javascript

Created by: rdn32

Add page for adding comment to feedback, for use when javascript is disabled.

Make the show/hide logic for comment form hinge on "showable" class rather than "form_comment" so that the form is always displayed on comment page. (Fix for https://aptivate.kanbantool.com/boards/5986-econsensus#tasks-1128515)