Integration with the new reaktiv library

[guillaume-mueller]

This new reactive library called reaktiv looks promising: see https://reaktiv.bui.app.

Now the author just called for ideas on how the API should be improved in order to have third-party libraries working better in combination: see buiapp/reaktiv#24. Maybe it would be interesting if you have anything to point out that you think about.

I've already wrote those regarding my use of python-socketio before: see buiapp/reaktiv#22.

Also especially async is still not yet fully established regarding how it should be exposed to the user: see buiapp/reaktiv#21.