experimental: Rich Text list item support

[istarkov]

Description

ref #4595

Bugs

• - Empty list items are not considered as editable

Steps for reproduction

1. click button
2. expect xyz

Code Review

• hi @kof, I need you to do
  • conceptual review (architecture, feature-correctness)
  • detailed review (read every line)
  • test it on preview

Before requesting a review

• made a self-review
• added inline comments where things may be not obvious (the "why", not "what")

Before merging

• tested locally and on preview environment (preview dev login: 0000)
• updated test cases document
• added tests
• if any new env variables are added, added them to .env file

[johnsicili]

Works.

I think it's a bit unintuitive to get out of the list. ie you have to use slash at the end.

Would be nice to auto exit after entering within an empty list item.

1. hello (now I hit enter)
2. (I hit enter again and this gets removed and p gets added)

[istarkov]

Moved here #4595