Make package PEP 561 compliant (#75)

* Add py.typed to comply with PEP 561

* Add Typing :: Typed to setup.classifiers

Author: zero323

pytest_mypy_plugins/py.typed

@@ -28,6 +28,9 @@
     entry_points={"pytest11": ["pytest-mypy-plugins = pytest_mypy_plugins.collect"]},
     install_requires=dependencies,
     python_requires=">=3.6",
+    package_data={
+        "pytest_mypy_plugins": ["py.typed"],
+    },
     classifiers=[
         "Development Status :: 3 - Alpha",
         "License :: OSI Approved :: MIT License",
@@ -36,5 +39,6 @@
         "Programming Language :: Python :: 3.8",
         "Programming Language :: Python :: 3.9",
         "Programming Language :: Python :: 3.10",
+        "Typing :: Typed",
     ],
 )