first add files

lib/Crypto/Cipher/Salsa20.pyi

@@ -0,0 +1,27 @@
+from typing import Union, Tuple, Optional, overload
+
+
+Buffer = Union[bytes, bytearray, memoryview]
+
+class Salsa20Cipher:
+    nonce: bytes
+    block_size: int
+    key_size: int
+
+    def __init__(self,
+                 key: Buffer,
+                 nonce: Buffer) -> None: ...
+    @overload
+    def encrypt(self, plaintext: Buffer) -> bytes: ...
+    @overload
+    def encrypt(self, plaintext: Buffer, output: Union[bytearray, memoryview]) -> None: ...
+    @overload
+    def decrypt(self, plaintext: Buffer) -> bytes: ...
+    @overload
+    def decrypt(self, plaintext: Buffer, output: Union[bytearray, memoryview]) -> None: ...
+
+def new(key: Buffer, nonce: Optional[Buffer] = ...) -> Salsa20Cipher: ...
+
+block_size: int
+key_size: Tuple[int, int]
+