Allow comparison of multiple values

[fliphess]

Hi!

This is a feature request:

I'd love to be able to make a comparison between multiple keys in a kubernetes file. For example: ensure that multiple values are equal or use jmespath in both key and values:

  assertions:
  - key: spec.values[].image.tag
    op: eq
    value_from: 
      key: spec.values.mainVersion

or

  assertions:
  - key: spec.values.somevalue
    op: eq
    value_from: 
      key: spec.values.some_other_value