🎨 add CodeQL badge

README.md

@@ -3,6 +3,7 @@
 [![PyPI Latest Release](https://img.shields.io/pypi/v/tsdownsample.svg)](https://pypi.org/project/tsdownsample/)
 [![support-version](https://img.shields.io/pypi/pyversions/tsdownsample)](https://img.shields.io/pypi/pyversions/tsdownsample)
 [![Downloads](https://pepy.tech/badge/tsdownsample)](https://pepy.tech/project/tsdownsample)
+[![CodeQL](https://github.com/predict-idlab/tsdownsample/actions/workflows/codeql.yml/badge.svg)](https://github.com/predict-idlab/tsdownsample/actions/workflows/codeql.yml)
 [![Testing](https://github.com/predict-idlab/tsdownsample/actions/workflows/ci-downsample_rs.yml/badge.svg)](https://github.com/predict-idlab/tsdownsample/actions/workflows/ci-downsample_rs.yml)
 [![Testing](https://github.com/predict-idlab/tsdownsample/actions/workflows/ci-tsdownsample.yml/badge.svg)](https://github.com/predict-idlab/tsdownsample/actions/workflows/ci-tsdownsample.yml)
 <!-- TODO: codecov -->