Maintaining the module - Drupal 9 release

Dear maintainers,

The Advanced Text Formatter is being used on some 3100 sites at least on Drupal 8.

There are Drupal 9 compatibility issues. You can see them on the following ticket(s):
#3139547: Automated Drupal Rector fixes
#3117655: Add core version requirement support for drupal 9

If you unable to maintain the module to fix these issues, I'm willing to get maintain it so we release the D9 version ASAP.
If you're able to, it would be great if you can please review the patch provided in the ticket(s).

Note that we're using this module as part of the Varbase distribution. So it's of vital importance to us to get it to Drupal 9. That's why we're willing to maintain the module if you're unable to.

Thanks!