test: add conftest.py to register example marker

- Adds a conftest.py file in tests/examples to register the pytest.mark.example marker
- Eliminates pytest warnings about unknown markers in example tests
- Improves test output by removing noise from warnings

Author: tony

tests/examples/conftest.py

@@ -0,0 +1,13 @@
+"""Pytest configuration for example tests."""
+
+from __future__ import annotations
+
+import pytest  # noqa: F401 - Need this import for pytest hooks to work
+
+
+def pytest_configure(config) -> None:
+    """Register custom pytest markers."""
+    config.addinivalue_line(
+        "markers",
+        "example: mark a test as an example that demonstrates how to use the library",
+    )