Add preserve tags option to formatter

Please reroll against 2.0.x!

Also looks like a duplicate of #2901579: Allow the possibility to specify which tags to be stripped when Strip HTML checkbox is ticked. (allow-list) to me?

We are hesitant to add additional configuration fields to the Smart Trim UI.

I think that this is a bit of an edge case, but I would like to see if this functionality could be implemented in a separate module using hook_form_alter() and an updated hook_smart_trim_link_modify() (once #3357315: hook_smart_trim_link_modify() does not do anything useful) is fixed.

If not, it would make sense to consider what else we could do to make this sort of thing possible in a separate module (maybe adding an additional hook somewhere?)

So, for now, let's mark this as "Postponed" until #3357315: hook_smart_trim_link_modify() does not do anything useful is fixed.

-mike

This is indeed a duplicate of https://www.drupal.org/project/smart_trim/issues/2901579
To upgrade from this patch to the MR in 2901579

Updated patch 3 to work with changes from 2.1.1.