Function resolveWindow

resolveWindow(
handles: ReadonlyMap<string, MountedApplet>,
event: MessageEvent,
): WindowResolution | null
Resolve the window a window-level message came from, from the shell's own registry and never from the message.
Parameters
- handles: ReadonlyMap<string, MountedApplet>
  Live applet handles.
- event: MessageEvent
  The window-level message.
Returns WindowResolution | null
The window and its applet, or null for unregistered sources.
Example
```
resolveWindow(handles, event)?.napplet; // 'chat'
```