Feature Request: Blockly Realtime Collaboration Coding

Is your feature request related to a problem? Please describe.
When working in groups online, it would be great to have some kind of real time collaboration feature.

Describe the solution you'd like
Blocky already has a working RTC solution: https://github.com/google/blockly-samples/tree/master/examples/blockly-rtc
I would really love to see this integrated in PXT.

Describe alternatives you've considered
I tried a pretty basic implementation using Yjs and syncing the project from outside trough the iFrame change and import events: https://go.calliope.cc/beta/rtc/#room1 (anything after # defines a own room)

That is working as long as the changes are not simultaneous. Since it is reloading the whole project for each update, the sidebar gets closed, the viewport resets and any focus is lost. If it will be possible to just update parts of a project that might be solvable things. But I think a better approach is a direct integration into pxt using blockly-rtc.

Start by reviewing the Blockly RTC example linked in the issue and the referenced Yjs iframe-based implementation. Trace how PXT currently handles project change and import events. Done would mean integrated real-time collaboration that supports simultaneous edits without reloading the whole project or losing the sidebar, viewport, or focus.