ci: GHA basic format & pre-commit (#2309)

diff --git a/tests/test_eval.py b/tests/test_eval.py
index 94228e7..66bec55 100644
--- a/tests/test_eval.py
+++ b/tests/test_eval.py
@@ -1,3 +1,4 @@
+# -*- coding: utf-8 -*-
 import os
 import pytest
 from pybind11_tests import eval_ as m