Configure Nox and basic Poetry support

- Use new structure for code blocks in README

noxfile.py

@@ -0,0 +1,13 @@
+from typing import TYPE_CHECKING
+
+import nox
+
+
+if TYPE_CHECKING:
+    from nox.sessions import Session
+
+python_versions = ["3.9", "3.10", "3.11", "3.12", "3.13"]
+
+@nox.session(python=python_versions, reuse_venv=True)
+def tests(session: "Session") -> None:
+    _ = session.run("python", "snippets/2_tricky_strings.py")