Update github action README.md to describe skip action

[lauramurgatroyd]

Description

Example Usage

Changes

Testing you performed

Please add any demo scripts to https://github.com/TomographicImaging/CIL-Demos/tree/main/misc

Related issues/links

Checklist

• I have performed a self-review of my code
• I have added docstrings in line with the guidance in the developer guide
• I have updated the relevant documentation
• I have implemented unit tests that cover any new or modified functionality
• CHANGELOG.md has been updated with any functionality change
• Request review from all relevant developers
• Change pull request label to 'Waiting for review'

Contribution Notes

Please read and adhere to the developer guide and local patterns and conventions.

• The content of this Pull Request (the Contribution) is intentionally submitted for inclusion in CIL (the Work) under the terms and conditions of the Apache-2.0 License
• I confirm that the contribution does not violate any intellectual property rights of third parties

[MargaretDuff]

I'm not sure that the skip.yml works as described e.g. https://github.com/TomographicImaging/CIL/actions/runs/12706378218/job/35419221004 was just the last changelog.md change on #2006 and everything ran

[lauramurgatroyd]

It is based on files edited in the PR not the commit

[MargaretDuff]

Thanks @lauramurgatroyd - that makes more sense - e.g. in this PR #1833 - it seems to be working!

[MargaretDuff]

Thanks @lauramurgatroyd