Add tkinter Event class (#4200)

stdlib/3/tkinter/__init__.pyi

@@ -1,4 +1,5 @@
 import sys
+from enum import Enum
 from types import TracebackType
 from typing import Any, Optional, Dict, Callable, Tuple, Type, Union
 from tkinter.constants import *  # noqa: F403
@@ -11,7 +12,69 @@ READABLE: Any
 WRITABLE: Any
 EXCEPTION: Any
 
-class Event: ...
+if sys.version_info >= (3, 6):
+    class EventType(str, Enum):
+        Activate: str = ...
+        ButtonPress: str = ...
+        ButtonRelease: str = ...
+        Circulate: str = ...
+        CirculateRequest: str = ...
+        ClientMessage: str = ...
+        Colormap: str = ...
+        Configure: str = ...
+        ConfigureRequest: str = ...
+        Create: str = ...
+        Deactivate: str = ...
+        Destroy: str = ...
+        Enter: str = ...
+        Expose: str = ...
+        FocusIn: str = ...
+        FocusOut: str = ...
+        GraphicsExpose: str = ...
+        Gravity: str = ...
+        KeyPress: str = ...
+        KeyRelease: str = ...
+        Keymap: str = ...
+        Leave: str = ...
+        Map: str = ...
+        MapRequest: str = ...
+        Mapping: str = ...
+        Motion: str = ...
+        MouseWheel: str = ...
+        NoExpose: str = ...
+        Property: str = ...
+        Reparent: str = ...
+        ResizeRequest: str = ...
+        Selection: str = ...
+        SelectionClear: str = ...
+        SelectionRequest: str = ...
+        Unmap: str = ...
+        VirtualEvent: str = ...
+        Visibility: str = ...
+
+class Event:
+    serial: int
+    num: int
+    focus: bool
+    height: int
+    width: int
+    keycode: int
+    state: Union[int, str]
+    time: int
+    x: int
+    y: int
+    x_root: int
+    y_root: int
+    char: str
+    send_event: bool
+    keysym: str
+    keysym_num: int
+    if sys.version_info >= (3, 6):
+        type: EventType
+    else:
+        type: str
+    widget: Misc
+    delta: int
 
 def NoDefaultRoot(): ...