first add files

lib/Crypto/Hash/cSHAKE256.pyi

@@ -0,0 +1,8 @@
+from typing import Union, Optional
+
+from Crypto.Hash.cSHAKE128 import cSHAKE_XOF
+
+Buffer = Union[bytes, bytearray, memoryview]
+
+def new(data:     Optional[Buffer] = ...,
+        custom:   Optional[Buffer] = ...) -> cSHAKE_XOF: ...