graphics: respect Windows dark mode (#765)

Only affects the caption bar.

Should work for:

- [x] standalone configurator
- [x] dx9 games, including multi-window games like gitadora
- [x] Unity games

src/spice2x/cfg/configurator_wnd.cpp

@@ -12,6 +12,7 @@
 #include "overlay/overlay.h"
 #include "util/logging.h"
 #include "util/precise_timer.h"
+#include "util/utils.h"
 #include "cfg/configurator.h"
 
 #include "icon.h"
@@ -214,6 +215,8 @@ cfg::ConfiguratorWindow::ConfiguratorWindow() {
 
     if (this->hWnd) {
         overlay::USE_WM_CHAR_FOR_IMGUI_CHAR_INPUT = true;
+        // force dark title bar
+        set_window_dark_titlebar(this->hWnd, true);
     }
 }