Adds initial universe seeding

[marimeireles]

Inspired on meta's #12.

One runs it with npm run universe:load default for the default seeding. Similar to the golden-state!

The most important documentation doc for this PR is creating-universes.md:

One creates an universe by:

npm run cli -- universe create team-project \
  --name "Team Project" \
  --description "Alice and Bob collaborating on a project" \
  --personas alice,bob

then uses the CLIs to add data to it.

Then runs load.

This will create a JSON file that the typescript will use to populate the browser.

[marimeireles]

@bgrins would be nice to be part of the repo so I can accept the workflow approvals.
Also, I'm thinking I should also add tests, but feel a little unsure about doing this w/o your OK on whether this is a good direction?