nhn/tui.editor ? reverse-engineered prompt

Build me a markdown editor app that lets people write in both plain markdown and a rich text view, and switch between them anytime. It should feel polished, with live preview, synced scrolling, a toolbar for common formatting, dark mode, and a viewer only mode for reading content without editing.

I also want it to support the useful stuff people expect in GitHub style markdown, like tables, code blocks with syntax highlighting, and easy copy and paste from other apps. If it makes sense, add support for extra plugins so charts and UML diagrams can render from special code blocks, plus a few other extensions like colored text and merged table cells.

Make it usable in plain JavaScript, and if you can, include wrappers for React and Vue too. Use the current docs online if you need to confirm behavior or examples.