Re-organize directory structure (#4971)

See discussion in #2491

Co-authored-by: Ivan Levkivskyi <ilevkivskyi@dropbox.com>

stdlib/email/charset.pyi

@@ -0,0 +1,28 @@
+from typing import Any, Iterator, List, Optional
+
+QP: int  # undocumented
+BASE64: int  # undocumented
+SHORTEST: int  # undocumented
+
+class Charset:
+    input_charset: str
+    header_encoding: int
+    body_encoding: int
+    output_charset: Optional[str]
+    input_codec: Optional[str]
+    output_codec: Optional[str]
+    def __init__(self, input_charset: str = ...) -> None: ...
+    def get_body_encoding(self) -> str: ...
+    def get_output_charset(self) -> Optional[str]: ...
+    def header_encode(self, string: str) -> str: ...
+    def header_encode_lines(self, string: str, maxlengths: Iterator[int]) -> List[str]: ...
+    def body_encode(self, string: str) -> str: ...
+    def __str__(self) -> str: ...
+    def __eq__(self, other: Any) -> bool: ...
+    def __ne__(self, other: Any) -> bool: ...
+
+def add_charset(
+    charset: str, header_enc: Optional[int] = ..., body_enc: Optional[int] = ..., output_charset: Optional[str] = ...
+) -> None: ...
+def add_alias(alias: str, canonical: str) -> None: ...
+def add_codec(charset: str, codecname: str) -> None: ...