[Feature Request] Make the editor work with Grammerly

[jefferyyuan]

• Spelling and Grammar check is important when wiring.
• It would be good to make the left side editor work with Grammarly: maybe just add contenteditable="true"
• Even better, if we can make the preview editable and work with Grammarly, so we can fix spelling error and grammar at the preview section and the change can be synced with the markdown source.

Thanks.