Continuous integration for tracking development branches

[jimpick]

We could set up CI pipelines to track development branches of Lotus and automatically
publish schema JSON files somewhere.

I think we should only check in schema files into this package for major branches.

For development branches, we could publish schema files and an index to IPFS and implement a schema loader to fetch a schema that matches a particular Lotus version (perhaps based on the git hash retrieved via the Version JSON-API method).