fix: Remove ignore_users authored items from markdown results

[zkoppert]

Pull Request

fixes #365

Proposed Changes

This pull request introduces three changes to remove issues and pull requests authored by ignored users. The three changes are

1. updating the README.md to clarify the behavior of the IGNORE_USERS setting
2. modifying the issue_metrics.py file to filter out issues from ignored users
3. adding new tests to ensure the functionality works correctly

Readiness Checklist

Author/Contributor

• If documentation is needed for this change, has that been included in this pull request
• run make lint and fix any issues that you have introduced
• run make test and ensure you have test coverage for the lines you are introducing
• If publishing new data to the public (scorecards, security scan results, code quality results, live dashboards, etc.), please request review from @jeffrey-luszcz

Reviewer

• Label as either fix, documentation, enhancement, infrastructure, maintenance, or breaking

[jmeridth]

Very nice. Love the test coverage.