docs(readme): add pypi downloads badge to readme (#243)

Fixes: #238

README.md

@@ -6,7 +6,7 @@ now with additional features and ongoing maintenance.
 | __CI__ | [![pre-commit.ci status][pre-commit-ci-badge]][pre-commit-ci-status] [![ci][ci-badge]][ci-workflow] [![coverage][coverage-badge]][ci-workflow] |
 | :--- | :--- |
 | __Docs__ | [![docs][docs-badge]][docs-workflow] |
-| __Package__ | [![pypi-version][pypi-version-badge]][pypi-url] [![pypi-python-versions][pypi-python-versions-badge]][pypi-url]|
+| __Package__ | [![pypi-version][pypi-version-badge]][pypi-url] [![pypi-python-versions][pypi-python-versions-badge]][pypi-url] [![pypi-downloads][pypi-downloads-badge]][pypi-url] |
 | __Meta__ | [![OpenSSF Scorecard][scorecard-badge]][scorecard-url] [![hatch][hatch-badge]][hatch] [![ruff][ruff-badge]][ruff] [![mypy][mypy-badge]][mypy] [![License][license-badge]][license] |
 
 oaipmh-scythe is a lightweight [OAI-PMH](http://www.openarchives.org/OAI/openarchivesprotocol.html)