Support complete HTML markup

Patch #3 works well for me, thanks!

The patch from #3 applies and works as expected on Drupal version 9.5.10 and mail_safety 2.0.0

Works for me, amazing difference doing it this way.
The preview in the iframe is now an exact replica of how it looks in my inbox. This is the way.

sjerdo → changed the visibility of the branch 3281615-support-complete-html to hidden.

Automatically closed - issue fixed for 2 weeks with no activity.