Allow suppression of actual diff by `kind`

[jrnt30]

First of all, super helpful tool that we use quite often! Thanks for your time.

We would love to integrate helm-diff a bit tighter in our CI/CD pipeline but have a bit of an issue where we don't want to expose the actual diff of a credential to the output.

It would be extremely handy to be able to blacklist a set of kind resources that would only show a CONTENT CHANGED type message if anything internal had changed instead of actually displaying the contents.