Improve notebook markdown cell rendering

[msujew]

What it does

Improves the markdown rendering logic of markdown cells by rendering the HTML element directly into the markdown cell without using innerHTML manipulation.

This allows to keep the mouse based events that the markdown renderer attaches to the HTML elements. Elements such as links are broken when attempting to use innerHTML manipulation.

How to test

1. Create a new markdown cell and set the content:

## Heading 2

### Heading 3

This is a paragraph of text.

- Item 1
- Item 2
- Item 3

**Bold text**

*Italic text*

[Link to Google](https://www.google.com)

2. Click on the link and ensure that it opens in a new browser tab.
3. Create a new empty markdown cell and finish editing. Double clicking the cell should enter edit mode.

Review checklist

• As an author, I have thoroughly tested my changes and carefully followed the review guidelines

Reminder for reviewers

• As a reviewer, I agree to behave in accordance with the review guidelines

[jonah-iden]

nice solution. Works great! Also seems to be more performant according to some articles. Maybe we should do the same with the cell editor