PYTHON-3214 Fix typing markers not being included in the distribution (#921)

MANIFEST.in

@@ -12,6 +12,3 @@ include tools/README.rst
 recursive-include test *.pem
 recursive-include test *.py
 recursive-include bson *.h
-include bson/py.typed
-include gridfs/py.typed
-include pymongo/py.typed

setup.py

@@ -295,7 +295,14 @@ if sys.platform == "win32":
 else:
     extras_require["gssapi"] = ["pykerberos"]
 
-extra_opts = {"packages": ["bson", "pymongo", "gridfs"]}
+extra_opts = {
+    "packages": ["bson", "pymongo", "gridfs"],
+    "package_data": {
+        "bson": ["py.typed"],
+        "pymongo": ["py.typed"],
+        "gridfs": ["py.typed"],
+    },
+}
 
 if "--no_ext" in sys.argv:
     sys.argv.remove("--no_ext")