Document pre-commit

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claude-sonnet-4-6: <ide_opened_file>The user opened the file ./docs/contributing.rst in the IDE. This may or may not be related to the current task.</ide_opened_file> add pre-commit to the prerequisites and install steps

Author: niccokunzmann

CONTRIBUTING.md

@@ -0,0 +1,2 @@
+# Contribution Guide
+

docs/contributing.rst

@@ -9,6 +9,7 @@ Prerequisites
 - Python 3.10 or later
 - Git
 - ``make``
+- `pre-commit <https://pre-commit.com/#install>`_
 
 Getting started
 ---------------
@@ -31,6 +32,12 @@ This runs ``python3 -m venv .venv`` and then ``pip install -e ".[dev]"``,
 which installs ``pytest``, ``sphinx``, and ``sphinx-autobuild`` alongside the
 extension itself.
 
+Install the pre-commit hooks so they run automatically on every commit:
+
+.. code-block:: bash
+
+    pre-commit install
+
 Building the docs
 -----------------