feat: adding docs change validation step in reuseable CI

[siddharth-khatsuriya]

Description

Added a new job validate-docs-change.
This job will attempt to serve the documentation and fail if there are any errors.
If errors occur, they will be printed in the check logs step.

Another stage, enforce-docs-changes, reviews the result of validate-docs-change and uses run metadata to determine whether the job should fail the pipeline.

When the PR targets the main branch, enforce-docs-changes will enforce failure on broken documentation and block merge.
For other branches, it serves as an indicator of documentation issues without blocking the merge.

Checklist

• README.md has been updated or is not required
• push trigger tests
• manual release test
• automated releases test
• pull request trigger tests
• schedule trigger tests
• workflow errors/warnings reviewed and addressed

Testing done

(for each selected checkbox, the corresponding test results link should be listed here)