docs: update readme to show unused reason

[yonahd]

What this PR does / why we need it?

PR Checklist

• [ ] This PR adds K8s exceptions (false positives)
• [ ] This PR adds new code
• [ ] This PR includes tests for new/existing code
• [x] This PR adds docs

GitHub Issue

Closes [XX-XX]

Notes for your reviewers

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 41.34%. Comparing base (ced2ef2) to head (6ae2f61).

:exclamation: Your organization needs to install the Codecov GitHub app to enable full functionality.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #317 +/- ## ======================================= Coverage 41.34% 41.34% ======================================= Files 61 61 Lines 3212 3212 ======================================= Hits 1328 1328 Misses 1671 1671 Partials 213 213 ```

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.