windows: Dock menu impl 2 (#26010)

Closes #ISSUE

Release Notes:

- N/A *or* Added/Fixed/Improved ...

crates/gpui/src/platform/windows/events.rs

@@ -22,6 +22,7 @@ use crate::*;
 pub(crate) const WM_GPUI_CURSOR_STYLE_CHANGED: u32 = WM_USER + 1;
 pub(crate) const WM_GPUI_CLOSE_ONE_WINDOW: u32 = WM_USER + 2;
 pub(crate) const WM_GPUI_TASK_DISPATCHED_ON_MAIN_THREAD: u32 = WM_USER + 3;
+pub(crate) const WM_GPUI_DOCK_MENU_ACTION: u32 = WM_USER + 4;
 
 const SIZE_MOVE_LOOP_TIMER_ID: usize = 1;
 const AUTO_HIDE_TASKBAR_THICKNESS_PX: i32 = 1;