Re-organize directory structure (#4971)

See discussion in #2491

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

stdlib/json/encoder.pyi

@@ -0,0 +1,27 @@
+from typing import Any, Callable, Iterator, Optional, Tuple
+
+class JSONEncoder:
+    item_separator: str
+    key_separator: str
+
+    skipkeys: bool
+    ensure_ascii: bool
+    check_circular: bool
+    allow_nan: bool
+    sort_keys: bool
+    indent: int
+    def __init__(
+        self,
+        *,
+        skipkeys: bool = ...,
+        ensure_ascii: bool = ...,
+        check_circular: bool = ...,
+        allow_nan: bool = ...,
+        sort_keys: bool = ...,
+        indent: Optional[int] = ...,
+        separators: Optional[Tuple[str, str]] = ...,
+        default: Optional[Callable[..., Any]] = ...,
+    ) -> None: ...
+    def default(self, o: Any) -> Any: ...
+    def encode(self, o: Any) -> str: ...
+    def iterencode(self, o: Any, _one_shot: bool = ...) -> Iterator[str]: ...