don't attempt to start steam overlay when vrchat is running with --no-vr

WinApi.cs

@@ -15,5 +15,8 @@ namespace VRCX
 
         [DllImport("user32.dll")]
         public static extern IntPtr FindWindow(string lpClassName, string lpWindowName);
+
+        [DllImport("user32.dll", SetLastError = true)]
+        public static extern UInt32 GetWindowThreadProcessId(IntPtr hWnd, out Int32 lpdwProcessId);
     }
 }