TypeCellOS/BlockNote ? reverse-engineered prompt

I want a modern rich text editor for React, kind of like Notion, that lets me create and organize content in blocks. It should feel really smooth with animations, let users drag and drop blocks, nest them using tab and shift+tab, and have helpful placeholders. I’d like an easy way to format text and maybe a slash command menu to insert new block types. Collaboration in real time would be great too. The editor should be polished and ready to drop into my app, with a nice default look. Please build this with React and make it easy to use—just a few lines to get started ideally. Check online for the latest docs if you need more details.