Participation to the task forces

Hi all,

As decided during our last WG meeting, I have created the 3 task forces.
It seems that you can not join a task force on your own, I have to add 
you manually.

So I have created a wiki page, where everybody can add their name:

     https://github.com/w3c/rdf-star-wg/wiki/Task-forces


(I initially created a file in docs, but PRs to add your names would 
have resulted in many conflicts, so the wiki seemed safer in that case)

I will monitor the page and add people as we go.

   best