clients: Add window_is_transient() helper to the toy toolkit window

clients/window.c

@@ -3976,6 +3976,12 @@ window_is_fullscreen(struct window *window)
 	return window->type == TYPE_FULLSCREEN;
 }
 
+int
+window_is_transient(struct window *window)
+{
+	return window->type == TYPE_TRANSIENT;
+}
+
 static void
 configure_request_completed(void *data, struct wl_callback *callback, uint32_t  time)
 {

clients/window.h

@@ -357,6 +357,9 @@ display_surface_damage(struct display *display, cairo_surface_t *cairo_surface,
 void
 window_set_buffer_type(struct window *window, enum window_buffer_type type);
 
+int
+window_is_transient(struct window *window);
+
 int
 window_is_fullscreen(struct window *window);