Re-organize directory structure (#4971)

See discussion in #2491

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

stdlib/urllib/robotparser.pyi

@@ -0,0 +1,19 @@
+import sys
+from typing import Iterable, List, NamedTuple, Optional
+
+class _RequestRate(NamedTuple):
+    requests: int
+    seconds: int
+
+class RobotFileParser:
+    def __init__(self, url: str = ...) -> None: ...
+    def set_url(self, url: str) -> None: ...
+    def read(self) -> None: ...
+    def parse(self, lines: Iterable[str]) -> None: ...
+    def can_fetch(self, user_agent: str, url: str) -> bool: ...
+    def mtime(self) -> int: ...
+    def modified(self) -> None: ...
+    def crawl_delay(self, useragent: str) -> Optional[str]: ...
+    def request_rate(self, useragent: str) -> Optional[_RequestRate]: ...
+    if sys.version_info >= (3, 8):
+        def site_maps(self) -> Optional[List[str]]: ...