add stub for importlib.resources (#1993)

Part of #1965

stdlib/3.7/importlib/resources.pyi

@@ -0,0 +1,22 @@
+import os
+
+from pathlib import Path
+from types import ModuleType
+from typing import ContextManager, Iterator, Union, BinaryIO, TextIO
+
+Package = Union[str, ModuleType]
+Resource = Union[str, os.PathLike]
+
+def open_binary(package: Package, resource: Resource) -> BinaryIO: ...
+def open_text(package: Package,
+              resource: Resource,
+              encoding: str = ...,
+              errors: str = ...) -> TextIO: ...
+def read_binary(package: Package, resource: Resource) -> bytes: ...
+def read_text(package: Package,
+              resource: Resource,
+              encoding: str = ...,
+              errors: str = ...) -> str: ...
+def path(package: Package, resource: Resource) -> ContextManager[Path]: ...
+def is_resource(package: Package, name: str) -> bool: ...
+def contents(package: Package) -> Iterator[str]: ...