Update Solid Process parts that are not already in the CG charter

[woutermont]

Creating this issue to address the concerns of @CxRes (cf. his comments in #323).

As I understand it, his concern is that with the CG charter itself only addressing the CG-related parts of the Solid Process, it is unclear

• where discussions concerning the broader Solid ecosystem can be conducted (in person); and
• what happens to the remainder of the Solid Process.

He therefore calls to clarify these points, by also updating the other parts of the Process. I'm fully with this, so let's discuss what needs to be changed/added.

@CxRes, feel free to correct me if I have misrepresented your points of concern.