[PR Workflow] Add a linter rule to flag json parsing issues. Do not add the WaitForARMFeedback label until the author resolves the issue

If the open API spec is not well-formed JSON, none of the other automated checks would be able to run and there is no use of performing a review for PRs in this state. We would first like the author to fix the basic issues before proceeding with the review. The `WaitForARMFeedback` label can then be added later by the bot once the json parsing issue is addressed.