Describe how to search the catalog without intake esm

[rabernat]

As you know, intake esm can be buggy. It's important for users to know they have the option to do their own searching and aggregation.

I recommend you add a section on this page just before "Loading an ESM Collection" called "Manually Searching the Catalog". This could be based off the example in my blog post, using pandas. It would also be amazing to show how to search the bigquery table, rather than the CSV file. That's the direction we want to be heading.

[charlesbluca]

Thanks for the insight! Addressed the first point with #13.

I'm comfortable adding in a section on navigating the BigQuery console or command line tool, but we may need some more consideration on how users not associated with our GCP project can access the table, as right now it requires specific IAM roles - I'm sure this is subject to change if we move ownership of the table to Google and link it to the CMIP6 bucket.