tldraw + Liveblocks Yjs

WIP—it's a bit laggy. Improvements made by @jcollingj.

Set up Liveblocks

• Install all dependencies with npm install
• Create an account on liveblocks.io
• Copy your secret key from the dashboard
• Create an .env.local file and add your secret key as the LIVEBLOCKS_SECRET_KEY environment variable
• Run npm run dev and go to http://localhost:3000