feat: added support for excluding charts from testing

[RyanW8]

Works as expected when I tested locally, I started writing tests but got confused about snapshot testing. Would appreciate any pointers!

[revolunet]

@RyanW8 whats the issue with tests ?

i can run that on my repo : helm unittest charts/* -u to run and update snapshots

here's an exemple test :

suite: test xxx
tests:
  - it: should render
    asserts:
      - template: deployment.yaml
        hasDocuments:
          count: 1
      - template: deployment.yaml
        matchSnapshot:
          path: spec