meta: github action to check pull request files for svn info

[hkershaw-brown]

Description:

Github action to check for svn detritus in any changed files in the pull request.
Only checks changed and new files, primary goal is to prevent people putting new files with svn info, secondary goal is to remove svn info as we find it while the file is under review.

Fixes issue

Partial fix for #802

Types of changes

• 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)
• Documentation update
• Github action

Documentation changes needed?

• My change requires a change to the documentation.
  • I have updated the documentation accordingly.

Tests

Please describe any tests you ran to verify your changes.
Ran the action on pull requests on my fork of DART
Ran the bash though shellcheck

Checklist for merging

• Updated changelog entry
• Documentation updated
• Update conf.py

Checklist for release

• Merge into main
• Create release from the main branch with appropriate tag
• Delete feature-branch

Testing Datasets

• Dataset needed for testing available upon request
• Dataset download instructions included
• No dataset needed