docs: add mypy badge

README.md

@@ -1,7 +1,8 @@
 # RDFProxy
 
-![tests](https://github.com/acdh-oeaw/rdfproxy/actions/workflows/tests.yaml/badge.svg)
+![tests](https://github.com/acdh-oeaw/rdfproxy/actions/workflows/tests.yml/badge.svg)
 [![coverage](https://coveralls.io/repos/github/acdh-oeaw/rdfproxy/badge.svg?branch=main&kill_cache=1)](https://coveralls.io/github/acdh-oeaw/rdfproxy?branch=main&kill_cache=1)
+[![Checked with mypy](https://www.mypy-lang.org/static/mypy_badge.svg)](https://mypy-lang.org/)
 [![docs](https://github.com/acdh-oeaw/rdfproxy/actions/workflows/deploy-docs.yml/badge.svg)](https://acdh-oeaw.github.io/rdfproxy/)
 [![License: GPL v3](https://img.shields.io/badge/License-GPLv3-blue.svg)](https://www.gnu.org/licenses/gpl-3.0)
 [![Ruff](https://img.shields.io/endpoint?url=https://raw.githubusercontent.com/astral-sh/ruff/main/assets/badge/v2.json)](https://github.com/astral-sh/ruff)