update governance

[drammock]

Update our public governance document.

TODOs:

• now that new governance is adopted, set a deadline for current maintainer team members to volunteer for steering council. deadline is Nov 1 and was announced on Discord and maintainer email list
• Once steering council membership finalized, update doc/overview/people.rst
• the sections on "the project" and "institutional partners" were not included in the proposed restructuring. For now I've left them in place. If folks disagree with that course of action, I think we could summarize the "institutional partners" content at the start of the "institutional partners" list on doc/overview/people.rst instead.

[britta-wstnr]

LGTM.
Unified capitalization a bit more - hope I have caught all (most) things.

[sappelhoff]

the sections on "the project" and "institutional partners" were not included in the proposed restructuring. For now I've left them in place.

I agree with this. However note that I have not been employed by "Max Planck Institute für Bildungsforschung" since 2024-07-14. So I guess this triggered the "1 year grace period" for them until they are moved to "former partners". Shall I create an event for this on our mne steering council calendar?

EDIT: As institutional partners are typically tied to a steering council member, it would be good to put some processes in place that these steering council members keep track of adding / removing the institutional partners (and how, e.g., with calendar entries for removal).

[larsoner]

Marking for merge-when-green, thanks in advance @drammock !