Switch Markdown engine to markdown-it-py

[torbjornvatn]

As mentioned in #16435 will switching to markdown-it-py give much more advanced Markdown rendering and make it behave almost like to Github Flavored Markdown

closes: #16435

[torbjornvatn]

I would ideally find a way to remove the display: block; property from a <summary> inside a <display> to get a ‣ in front of the collapsible content just as here on Github. But I couldn't figure out how to change any of the CSS really 🤷🏼

Example:

Click to expand!

Heading

1. A numbered
2. list
   • With some
   • Sub bullets

[ferruzzi]

Looks like you may have missed running the pre-commit hooks before pushing it and black failed. If you close and reopen the PR it should re-trigger, or you'll have to wait for Someone With Power to manually re-trigger it.

Other than the formatting issues that black should catch and correct, that looks good to me.

[torbjornvatn]

Closing this to re-trigger the static checks in another PR