Update README for 2025

[lisad]

The README here is quite bare bones, and when we have some clarity around WG or CG processes and where this fits and what the roadmap is, then it would be very useful to add that to the README.

[nigini]

I believe it would be very helpful if we could also document a list of tasks/goals that are planned for a given period of time with main pointers (it would, for sure, lower the bar for contributions.)

[lisad]

Actually I'm more or less waiting for implementors, or a W3C WG, or both. I can update this issue with something more helpful for sure.