Accept memoryview in email.base64mime.body_encode (#16653)

Author: AlvaroBalbin

stdlib/email/base64mime.pyi

@@ -6,7 +6,7 @@ def header_length(bytearray: str | bytes | bytearray) -> int: ...
 def header_encode(header_bytes: str | ReadableBuffer, charset: str = "iso-8859-1") -> str: ...
 
 # First argument should be a buffer that supports slicing and len().
-def body_encode(s: bytes | bytearray, maxlinelen: int = 76, eol: str = "\n") -> str: ...
+def body_encode(s: bytes | bytearray | memoryview, maxlinelen: int = 76, eol: str = "\n") -> str: ...
 def decode(string: str | ReadableBuffer) -> bytes: ...
 
 body_decode = decode