first add files

lib/Crypto/Cipher/ChaCha20.pyi

@@ -0,0 +1,25 @@
+from typing import Union, overload
+
+Buffer = Union[bytes, bytearray, memoryview]
+
+def _HChaCha20(key: Buffer, nonce: Buffer) -> bytearray: ...
+
+class ChaCha20Cipher:
+    block_size: int
+    nonce: bytes
+
+    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 seek(self, position: int) -> None: ...
+
+def new(key: Buffer, nonce: Buffer = ...) -> ChaCha20Cipher: ...
+
+block_size: int
+key_size: int