Select all comments for potential notification

Problem/Motivation

Drupal core comes with a default comment type with machine name "comment".

Users can create other with other names.

If the Forum module is installed, there is another comment type with machine name "comment_forum".

Notifications are only sent about "comment".

Steps to reproduce

Install Notify and Forum.

Subscribe user to "forum", and enable comment notifications.

Create forum posts with comments.

Observe that no notifications are sent for these comments.

You can also inspect "Skip Flags".

Observe that "comment_forum" type comments are not listed.

Proposed resolution

Change public function selectContent() (in "Notify.php") to include all types contents in what is returned.