test: Add tests directory with a dummy test

For local and automated testing of the source code, the testing
folder is added. This includes all the tests that the module has to
go through. The project also uses pytest-cov, which can also create
coverage reports.

tests/test_import.py

@@ -0,0 +1,14 @@
+# -*- coding: utf-8 -*-
+# SPDX-FileCopyrightText: 2025 KUNBUS GmbH
+# SPDX-License-Identifier: GPL-2.0-or-later
+"""Test module import."""
+
+import unittest
+
+
+class ModuleImport(unittest.TestCase):
+    def test_import(self):
+        """Test the import of the module."""
+        import revpi_middleware
+
+        self.assertEqual(type(revpi_middleware.__version__), str)