Create GitHub Action for checking validity of Hubs

[annakrystalli]

Gtihub Action should check:

• [ ] hub_config directory: (#60)
  • [ ] contains appropriate and valid files
  • [ ] schema_versions are consistent across files
• [ ] Data contained in model-output are valid and consistent with the schema. This portion of the checks will deploy functions from hubValidate

A template GA file should be created with a function like use_github_action("hub-integrity") as per usethis GA functions.

[elray1]

See also https://github.com/Infectious-Disease-Modeling-Hubs/hubValidations/issues/83