Update `fleetctl preview` instructions to address workarounds for (1) docker-compose bug and (2) SSL requirement

[mikermcneil]

docker compose workaround

This will be a medium-to-long term thing until we can get around to fixing it in docker-compose (or if someone beats us to it)

• https://github.com/docker/compose/issues/7495
• Error with docker-compose: docker-credential-desktop not installed or not available in PATH docker/for-mac#3785

ssl requirement workaround

Currently, osquery requires SSL even in development, so Fleet also requires SSL. We've discussed some options to make the dev quickstart experience better here, but super short term, it would help to get the readme updated w/ instructions on how to get past this

[mikermcneil]

🤞 ssl requirement will be resolved if we figure out a way to do #504