Ensure mouse cursor shape is correct

Previously, the shape was only set on focus in events and when hovering
urls. However, on macOS there are no focus events generated when the
mouse moves between the window and the titlebar/menubar, thus causing
incorrect mouse shape.

Fix #4118

kitty/mouse.c

@@ -505,6 +505,7 @@ currently_pressed_button(void) {
 
 HANDLER(handle_event) {
     modifiers &= ~GLFW_LOCK_MASK;
+    set_mouse_cursor_for_screen(w->render_data.screen);
     if (button == -1) {
         button = currently_pressed_button();
         handle_move_event(w, button, modifiers, window_idx);