Deployed new features - markdown preview button, bug fixes

πŸ‘ Updated Markdown preview is here. Previously you hover your cursor outside of the text area to preview in rich text. Based on feedback and dogfooding, found that the hover preview tend to trigger 'jumpy' spurious previews. So now it's a preview button on the top editing toolbar.

βœ… Fixed some bugs where the raw text was overflowing out of preview mode.