CI: Document modifications do not require running all tests.

[tao12345666333]

Is there an existing issue for this?

• [X] I have searched the existing issues

Problem Statement

We have files that only contain documents. When we make changes to them, we don't need to run all tests.

e.g.

• README.md and other *.md
• docs
• keps

https://github.com/Kong/kubernetes-ingress-controller/actions/runs/6939756390?pr=5193

Proposed Solution

we can add a path filter.

• https://docs.github.com/en/actions/using-workflows/workflow-syntax-for-github-actions#example-excluding-paths
• https://github.com/dorny/paths-filter

Additional information

No response

Acceptance Criteria

No response

[programmer04]

Reopened by revert done in #5225