Allow ImGui to process events if the overlay is hidden

This is used for the notifications when overlay is off.

overlay_experimental/windows/Windows_Hook.cpp

@@ -133,9 +133,9 @@ LRESULT CALLBACK Windows_Hook::HookWndProc(HWND hWnd, UINT uMsg, WPARAM wParam,
         }
     }
 
+    ImGui_ImplWin32_WndProcHandler(hWnd, uMsg, wParam, lParam);
     if (show)
     {
-        ImGui_ImplWin32_WndProcHandler(hWnd, uMsg, wParam, lParam);
         if (IgnoreMsg(uMsg))
             return 0;
     }