Use check-jsonschema to validate readthedocs config

[oraNod]

It's probably fine but would be a good idea to validate against the jsonschema too: https://github.com/ansible/awx-plugins/blob/814eec16b21f8bacd258a11eb5a7c8f866128b84/.pre-commit-config.yaml#L87. Perhaps, you could look into integrating it?

Originally posted by @webknjaz in ansible-community/package-doc-builds#8 (comment)