Doesn't seem to work on Reddit if the markdown editer is selected

**Describe the bug**
If you switch the comment or post textbox to the markdown editor then no spelling or grammar errors are picked up.

**To Reproduce**
Steps to reproduce the behavior:
1. Go to Reddit
2. Create a post with a spelling mistake in it
3. Switch the editor between markdown and rich text
4. The mistake is only highlighted in rich text mode

**Expected behavior**
Should highlight the error in either mode

**Screenshots**
https://github.com/user-attachments/assets/4e27aec1-908a-4a9a-aaf4-c281083fed51

**Platform**
Firefox

Start by reproducing the issue in Firefox on a Reddit post or comment, switching between rich text and markdown editors with a spelling mistake. Trace the editor integration from the browser extension entry points; done means spelling and grammar errors are highlighted in both editor modes.

Written by the indexing model from the issue text.