uxtheme: Add stub for IsDarkModeAllowedForWindow.

dlls/uxtheme/system.c

@@ -1315,3 +1315,13 @@ int WINAPI SetPreferredAppMode(int app_mode)
     FIXME("%d: stub\n", app_mode);
     return 0;
 }
+
+/**********************************************************************
+ *      IsDarkModeAllowedForWindow                        (UXTHEME.137)
+ *
+ */
+BOOL WINAPI IsDarkModeAllowedForWindow(HWND hwnd)
+{
+    FIXME("%p: stub\n", hwnd);
+    return FALSE;
+}

dlls/uxtheme/uxtheme.spec

@@ -46,6 +46,7 @@
 132 stdcall -noname ShouldAppsUseDarkMode()
 133 stdcall -noname AllowDarkModeForWindow(ptr long)
 135 stdcall -noname SetPreferredAppMode(long)
+137 stdcall -noname IsDarkModeAllowedForWindow(ptr)
 138 stdcall -noname ShouldSystemUseDarkMode()
 
 # Standard functions