Document the council's internal decision making process

[ehuss]

Currently it isn't clear exactly how or where decisions are made, or how they are communicated.

https://hackmd.io/@rust-leadership-council/ByAlBiHon contains a draft of some ideas on how to go about this.

This particularly includes where and how async decisions are made and publicized.

The RFC also suggests:

Establishing and agreeing on processes for faster decision-making for simple one-off operational matters, such as responding to emails reaching out to the Project.