add pre-commit config

.pre-commit-config.yaml

+repos:
+  # Using this mirror lets us use mypyc-compiled black, which is about 2x faster
+  - repo: https://github.com/psf/black-pre-commit-mirror
+    rev: 24.10.0
+    hooks:
+      - id: black
+        args: [--config=./pyproject.toml]
+        language_version: python3.10
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README.md

 # InSillyClo
 
 * dev https://insillyclo-main.dev.pasteur.cloud/
-* prod https://insillyclo-main.pasteur.cloud/
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+* prod https://insillyclo-main.pasteur.cloud/
+
+# Contributing
+
+Install Black to format sources, use pre-commit to prevent unformatted commit (which will be rejected by ci anyway)
+```shell
+pip install -r requirements-dev.txt
+pre-commit install
+```
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requirements-dev.txt

 black~=24.10.0
+pre-commit
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