Merge branch '47-readme-mypy-typechecking-badge' into 'master'

Resolve "Readme:  mypy typechecking badge"

Closes #47

See merge request !87

README.md

@@ -5,6 +5,7 @@ Pydisk-querybuilder (PQB)
 [![coverage report](https://gitlab.inria.fr/pydisk/querybuilder/badges/master/coverage.svg)](https://gitlab.inria.fr/pydisk/querybuilder/-/commits/master)
 [![Code style: black](https://img.shields.io/badge/code%20style-black-000000.svg)](https://github.com/psf/black)
 [![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)
+[![Checked with mypy](https://www.mypy-lang.org/static/mypy_badge.svg)](https://mypy-lang.org/)
 
 The goal of PQB is to offer a programmatic interface to various `SQL` dialects.
 It aims to replace stringified Schema definitions and Query writing.