Comments: Added HTML filter on load, tinymce elem filtering

- Added filter on load to help prevent potentially dangerous comment
  HTML in DB at load time (if it gets passed input filtering, or is
  existing).
- Added TinyMCE valid_elements for input wysiwygs, to gracefully degrade
  content at point of user-view, rather than surprising the user by
  stripping content, which TinyMCE would show, post-save.

resources/js/wysiwyg/config.js

@@ -339,6 +339,7 @@ export function buildForInput(options) {
         toolbar: 'bold italic link bullist numlist',
         content_style: getContentStyle(options),
         file_picker_types: 'file',
+        valid_elements: 'p,a[href|title],ol,ul,li,strong,em,br',
         file_picker_callback: filePickerCallback,
         init_instance_callback(editor) {
             addCustomHeadContent(editor.getDoc());