first add files

lib/Crypto/Cipher/ARC4.pyi

@@ -0,0 +1,16 @@
+from typing import Any, Union, Iterable
+
+Buffer = Union[bytes, bytearray, memoryview]
+
+class ARC4Cipher:
+    block_size: int
+    key_size: int
+
+    def __init__(self, key: Buffer, *args: Any, **kwargs: Any) -> None: ...
+    def encrypt(self, plaintext: Buffer) -> bytes: ...
+    def decrypt(self, ciphertext: Buffer) -> bytes: ...
+
+def new(key: Buffer, drop : int = ...) -> ARC4Cipher: ...
+
+block_size: int
+key_size: Iterable[int]