Desktop,Mobile: Fix list renumbering in the Markdown editor resets the first list item number to 1

[personalizedrefrigerator]

Summary

This pull request fixes a bug originally reported on the forum.

Markdown lists can start on numbers greater than 1. However, the "indent" button on mobile and tab on desktop (which renumber list items when indenting a numbered list) reset the first list item to 1.

Behavior comparison

Original note:

2. This
3. is
4. a
5. test

Old output: After pressing "indent" for the second item:

1. This
	1. is
2. a
3. test

New output: After pressing "indent" for the second item:

2. This
	1. is
3. a
4. test

Testing plan

This pull request includes an automated test.

Additionally, this has been tested with the desktop app by:

1. Creating a note with the following content:

   2. This
   3. is
   4. a
   4. test
   

2. Moving the cursor to the line starting with 3..
3. Pressing tab.
4. Verifying that the note now has the following content:

   2. This
   	1. is
   3. a
   4. test