Move typing examples into tests

To prevent confusion

.github/PULL_REQUEST_TEMPLATE.md

@@ -11,7 +11,7 @@ If an item doesn't apply to your pull request, **check it anyway** to make it ap
 -->
 
 - [ ] Added **tests** for changed code.
-- [ ] **New or changed APIs** are added to [`typing_examples.py`](https://github.com/hynek/environ-config/blob/main/typing_examples.py).
+- [ ] **New or changed APIs** are added to our [typing examples](https://github.com/hynek/environ-config/blob/main/tests/typing/api.py) to ensure our external type hints are sound.
 - [ ] Updated **documentation** for changed code.
     - [ ] New functions/classes have to be added to `docs/api.md` by hand.
     - [ ] Changed/added classes/methods/functions have appropriate `versionadded`, `versionchanged`, or `deprecated` [directives](http://www.sphinx-doc.org/en/stable/markup/para.html#directive-versionadded).

noxfile.py

@@ -105,7 +105,7 @@ def coverage_report(session: nox.Session) -> None:
 def mypy(session: nox.Session) -> None:
     session.install(".", "mypy")
 
-    session.run("mypy", "typing_examples.py")
+    session.run("mypy", "tests/typing")
 
 
 @nox.session(python=DOCS_PYTHON)

pyproject.toml

@@ -29,6 +29,7 @@ classifiers = [
     "Programming Language :: Python :: 3.11",
     "Programming Language :: Python :: 3.12",
     "Topic :: Software Development :: Libraries :: Python Modules",
+    "Typing :: Typed",
 ]
 dependencies = ["attrs>=17.4.0", "importlib_metadata; python_version<'3.8'"]
 
@@ -109,6 +110,10 @@ ignore_missing_imports = true
 module = "tests.*"
 ignore_errors = true
 
+[[tool.mypy.overrides]]
+module = "tests.typing.*"
+ignore_errors = false
+
 
 [tool.hatch.metadata.hooks.fancy-pypi-readme]
 content-type = "text/markdown"