Decide on a maintenance plan for Drupal 7 version

Problem/Motivation

Drupal 7 is reaching end-of-life and is receiving security updates only. In practice, this module hasn't been actively maintained for Drupal 7 for awhile now. In order to be transparent and clean up the issue queue, it would be good to make a decision on what level of maintenance the Drupal 7 version receives.

Proposed resolution

Choose to maintain the Drupal 7 version of Commenty Notify for critical security issues only. Mark existing bugs and feature requests for Comment Notify 7.x-1.3 as "Closed, won't fix."

Remaining tasks

1. ❌ Decide on maintenance approach for Comment Notify 7.x-1.3
2. ❌ Update issue queue accordingly
3. ❌ Update project page describing the maintenance status