add simple-sops example

[epcim]

Description

Please include a summary of the changes and the related issue. Please also include relevant motivation and context. List any dependencies that are required for this change.

Fixes # (issue)
Related # (pr in kluctl.io repository)

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• New example (change which adds a new example)

All Submissions:

• A corresponding issue exists - sops decryption of kustomization.yml secrets from file directive kluctl#422
• Have you added a related PR to the kluctl.io repository
• Have you added an explanation of what your changes do and why you'd like us to include them?
• Have you followed the guidelines in our Contributing document?
• Have you checked to ensure there aren't other open Pull Requests for the same update/change?
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• Have you lint your code locally before submission?
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules
• All commits are signed off which certify that you created the patch and that you agree to the Developer Certificate of Origin