migrate configuration to PEP621 compatible config

- adapt documentation
- add wheel tests to check wheel contents.
- adapt pipeline to use pdm
- adapt autopub config
- add scripts as shortcuts to invoke tasks

pelican/tests/build_test/conftest.py

@@ -0,0 +1,7 @@
+def pytest_addoption(parser):
+    parser.addoption(
+        "--check-wheel",
+        action="store",
+        default=False,
+        help="Check wheel contents.",
+    )