tkinter: allow index to be "end" in Treeview.move (#13454)

Author: evantj

stdlib/tkinter/ttk.pyi

@@ -1100,7 +1100,7 @@ class Treeview(Widget, tkinter.XView, tkinter.YView):
         open: bool = ...,
         tags: str | list[str] | tuple[str, ...] = ...,
     ) -> None: ...
-    def move(self, item: str | int, parent: str, index: int) -> None: ...
+    def move(self, item: str | int, parent: str, index: int | Literal["end"]) -> None: ...
     reattach = move
     def next(self, item: str | int) -> str: ...  # returning empty string means last item
     def parent(self, item: str | int) -> str: ...