chore : added pytest as test optionnal dep

pyproject.toml

@@ -14,6 +14,11 @@ classifiers = [
     ]
 dynamic = ["version"] # defined in tool.setuptools_scm
 
+[project.optional-dependencies]
+test = [
+    "pytest"
+]
+
 [build-system]
 requires = [
     "setuptools>=64",