disable win single alt key event

Signed-off-by: bggRGjQaUbCoE <githubaccount56556@proton.me>

windows/runner/win32_window.cpp

@@ -179,6 +179,12 @@ Win32Window::MessageHandler(HWND hwnd,
                             WPARAM const wparam,
                             LPARAM const lparam) noexcept {
   switch (message) {
+    case WM_SYSCOMMAND:
+      if (wparam == SC_KEYMENU && (lparam >> 16) <= 0) {
+        return 0;
+      }
+    break;
+
     case WM_DESTROY:
       window_handle_ = nullptr;
       Destroy();