Add copyright boilerplate check

[embano1]

Description

• Runs copyright header check against every new/modified file
• Update files with missing copyright header (I did not change the ones in vim25 since those are copies from Go src)

Closes: #2749 #2713

Type of change

Please mark options that are relevant:

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to
  not work as expected)
• This change requires a documentation update
• Build related change

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Provide
instructions so we can reproduce. If applicable, please also list any relevant
details for your test configuration.

• Verified that Reviewdog fails when license header is not present in a .go file

Checklist:

• My code follows the CONTRIBUTION guidelines of
  this project
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• 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

[embano1]

@dougm I created two commits, one which adds missing header, the other one for the CI part to simplify your review.

[dougm]

lgtm