Add py.typed marker file for PEP 561

This allows type checkers like mypy to use the type hints in our code
when type-checking another project that imports this library.

README.rst

@@ -120,6 +120,7 @@ Version 1.7.1 (next version)
 * Added filtering support to the ``list`` subcommand.
 * Added a ``resource-info`` subcommand to display technical information about resources (more detailed than what is displayed by ``list`` and ``read``).
 * Added a ``raw-compress-info`` subcommand to display technical header information about standalone compressed resource data.
+* Made the library PEP 561-compliant by adding a py.typed file.
 * Fixed an incorrect ``AssertionError`` when using the ``--no-decompress`` command-line options.
 
 Version 1.7.0

setup.cfg

@@ -41,9 +41,16 @@ keywords =
 	macos
 
 [options]
+# mypy can only find type hints in the package if zip_safe is set to False,
+# see https://mypy.readthedocs.io/en/latest/installed_packages.html#making-pep-561-compatible-packages
+zip_safe = False
 python_requires = >=3.6
 packages = find:
 
+[options.package_data]
+rsrcfork =
+	py.typed
+
 [options.packages.find]
 include =
 	rsrcfork