feat: Show connection status in the UI if the websocket connection fails

I have noticed that there are no status indicators in the GUI to indicate when the websocket connection to the collab server has an error. This is confusing sometimes. Steps to reproduce: 1. Open excalidraw.com 2. Start collaboration 3. Open the link in another tab/browser 4. Disconnect your wifi Expectation: I would expect to see some indication somewhere in the UI that the websocket connection has been dropped and that the client is attempting to reconnect. Current behavior: The green 'collaboration' indicator still stays lit, and the number of connected peers remains the same, while errors get printed in the console each time socket.io tries to reconnect: Consequence: It looks like you are still connected to the server, even when you aren't. Possible fix: Here is how we could track the connection status. In Collab.tsx, the socket.io client is registered. See We could add listeners there for connect_error, connect and disconnect, accordin…