[markdown] when hitting enter/return in a list, automatically add new list item

Issue

When typing a markdown list it can be a little annoying to continually type the bullet/checkbox/number each time I add a new line. I'm so used to using other software that maintains the formatting on new lines.

Proposal

Maintain formatting of Markdown when new lines are entered.

This behaviour is for editing raw Markdown. The Content Editor currently has this behaviour of maintaining list formatting for a new line.

For example:

• If I add a bullet point and hit enter
• The next line should automatically start with a bullet point

We should do this for bullet lists, numbered lists, and tasks lists.

This is the same behavior in word processing software (Word, Google docs, slides, etc)