Package Authors should be able to validate their packages locally

**Describe the problem/challenge you have**

I'm building a PackageRepository image bundle containing several Packages in it locally. I would like to have a way to verify that all of them are correct before pushing the bundle to a registry and deploying them into my cluster.

**Describe the solution you'd like**

I would like to have a command line that I could execute locally to verify that the contents I've just created are valid and that when deploying them to the cluster I won't face any kind of syntax error.

**Potential list of things to validate**
- Validation of the structure of the CRs such as PackageMetadata CR and Package CR
- Optional validation on the recommended metadata for packages that go in PackageMetadata CR or the Package CR. (such as icon, description, categories, release notes, etc.) [Refer to #307]
- Before pushing a package repository bundle, validate the recommended directory structure

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