add (overwrite with) mypy stubs, if available

stdlib/3/hashlib.pyi

@@ -0,0 +1,25 @@
+# Stubs for hashlib
+
+# NOTE: These are incomplete!
+
+from abc import abstractmethod, ABCMeta
+import typing
+
+class Hash(metaclass=ABCMeta):
+    @abstractmethod
+    def update(self, arg: bytes) -> None: ...
+    @abstractmethod
+    def digest(self) -> bytes: ...
+    @abstractmethod
+    def hexdigest(self) -> str: ...
+    @abstractmethod
+    def copy(self) -> 'Hash': ...
+
+def md5(arg: bytes = None) -> Hash: ...
+def sha1(arg: bytes = None) -> Hash: ...
+def sha224(arg: bytes = None) -> Hash: ...
+def sha256(arg: bytes = None) -> Hash: ...
+def sha384(arg: bytes = None) -> Hash: ...
+def sha512(arg: bytes = None) -> Hash: ...
+
+def new(name: str, data: bytes = None) -> Hash: ...