Prepare and get consensus on charter

[jar398]

Continuing the discussion started here: #28 (comment)
and continued here: #28 (comment)

In my view, a charter could help in (at least) three ways:

1. Helps orient observers and newcomers to what the group is doing
2. Helps decide what is good use of meeting time (what is in scope)
3. Helps remind people in group of outside agreements (what we said we'd do)

As @dckc says, the README and the NLnet post constitute a draft charter, and together may be adequate.

• I was wondering, is the README up to date with current thinking? A lot has happened since it was written. Review.
• There are mentions of the Spritely and Agoric 'CapTP' protocols; these should be hyperlinked to something.
• There should be a link trail from the repo's README to the NLnet post (also as @dckc suggests). Maybe copy the post into the repo or even into the README, for tidiness.
• IMO whatever the charter is, there should be agreement by consensus that it is the charter, and declared as such in the repo.

[dckc]

Agoric has pushed its captp library down into our "endo" layer; endo is a collaboration between Agoric, MetaMask, and others:

• https://github.com/endojs/endo/tree/master/packages/captp; currently: 389733d

I started to make a PR to add links into the README here, but it wasn't obvious how to do so; I got a little stumped.

[jar398]

N.b. other charter-ish material, from 2021, is here