[Docs]: Improvements to developer guide

[tomvothecoder]

Doc location

https://github.com/E3SM-Project/simboard/blob/main/docs/developer/README.md

What is wrong or missing?

1. Automated Metadata Ingestion section needs information about how simboard ingestion state is maintained -- NERSC ingestion job create /var/lib/simboard-ingestion/state.json to keep track of ingestion
2. Link to Make commands for more useful tips -- maybe do this

Suggested update

No response

Extra context

No response