Document Caddy steps here

[ghost]

@ionutiorgulescu Can you open a PR to create some file like docs/caddy.md in this repo and document what you said in this slack thread: https://filecoinproject.slack.com/archives/C01BUANJA5R/p1603795612280200?thread_ts=1603768562.274700&cid=C01BUANJA5R

Don't change the caddy config on the proxy retrieval machine for now. These are just notes so we can do it later.

• Could you also look at the original Caddyfile proposed by Gui in https://github.com/filecoin-shipyard/browser-retrieval/wiki/Enable-CORS-on-a-Lotus-API and figure out what all those other directives are doing and why we do or don't need to put them in our Caddyfile?

[ionutiorgulescu]

About the CORS directives, I don't think we need them. Because we do our requests from a backend and we have direct connection to lotus. If we did our requests from a frontend we had this CORS problems and we should include this directives.