github actions to check for pangeo updates

[kdorheim]

Stitches relies on internal package data that represents a snapshot of the pangeo archive. This minimizes run time of the actual stitching process as a number of pre-stitching time-intensive steps (making the matching archive) have already been completed. However if the pangeo archive updates this may cause errors.

• add checks to make sure that we are stitching with up to date with the pangeo archive
• an updated internal data script that can be launched as a job on pic
• a potential idea is to add a github actions script that would launch on a semi-regular basis that would fail if pangeo updates which would notify us that it is time to rebuild the package data. Launching the rebuild of the package data might be too computationally expensive to run on github actions but checking the pangeo catalog should not be.