Powergate docs enhancments

[andrewxhill]

Just tracking a bunch of things we need to chip away at for powergate docs.

• [ ] Add example embedded in docstrings to js-powergate-client to match https://textileio.github.io/js-hub/docs/
• [ ] Possibly migrate to client docusaurus and add typechecked docstrings
• [ ] Pull in a bunch of the questions from #support and add docs sections
• [ ] Document basics of non-docker setups (bring your own lotus / ipfs nodes and how to setup properly)