Integrate Rockon validator to check Rockon related PRs

[Hooverdan96]

Since @StephenBrown2 donated his work on Rockon json file validation (https://github.com/rockstor/rockon-validator), there could be an opportunity as suggested by @phillxnet to include some high-level validation via Github actions when new PRs are submitted (or updates to existing PRs are pushed). This in turn could then lead to additional checks for the rockon-validator to make submissions more streamlined.