Add pre-commit badge

Author: flying-sheep

README.rst

@@ -1,15 +1,22 @@
-scanpydoc |pypi| |docs| |ci| |cov|
-==================================
+scanpydoc |pypi| |docs| |tests| |checks| |cov|
+==============================================
 
 A collection of Sphinx extensions similar to (but more flexible than) numpydoc.
 
 Check the self-documenting documentation at https://icb-scanpydoc.readthedocs-hosted.com
 
 .. |pypi| image:: https://img.shields.io/pypi/v/scanpydoc.svg
    :target: https://pypi.org/project/scanpydoc/
+   :alt: PiPI version
 .. |docs| image:: https://readthedocs.com/projects/icb-scanpydoc/badge/
    :target: https://icb-scanpydoc.readthedocs-hosted.com/
-.. |ci| image:: https://github.com/theislab/scanpydoc/actions/workflows/ci.yml/badge.svg
+   :alt: doc build status
+.. |tests| image:: https://github.com/theislab/scanpydoc/actions/workflows/ci.yml/badge.svg
    :target: https://github.com/theislab/scanpydoc/actions/workflows/ci.yml
+   :alt: python test status
+.. |checks| image:: https://results.pre-commit.ci/badge/github/theislab/scanpydoc/master.svg
+   :target: https://results.pre-commit.ci/latest/github/theislab/scanpydoc/master
+   :alt: pre-commit.ci status
 .. |cov| image:: https://codecov.io/gh/theislab/scanpydoc/branch/master/graph/badge.svg
    :target: https://codecov.io/gh/theislab/scanpydoc
+   :alt: coverage