**Is your feature request related to a problem? Please describe.**

Currently, the only way to show the About panel on macOS is by creating a `{role: 'about'}` menu item and click it. I need to be able to show it manually.

**Describe the solution you'd like**

Electron already has the method, so it's just about exposing this to JS and documenting it:

https://github.com/electron/electron/blob/8ba271efba691357ab1970c1a553b4e019125574/atom/browser/browser_mac.mm#L376

Would also be useful to be able to pass in the panel options directly to the method to override the defaults.

I would call the method: `app.showAboutPanel(options)`

**Describe alternatives you've considered**

None.
atom/browser/api/atom_api_app.cc
if (Browser::Get()->is_ready()) {
    args->ThrowError(
        "app.disableHardwareAcceleration() can only be called "
        "before app is ready");
    return;
  }
  content::GpuDataManager::GetInstance()->DisableHardwareAcceleration();
}
void App::DisableDomainBlockingFor3DAPIs(mate::Arguments* args) {
  if (Browser::Get()->is_ready()) {
    args->ThrowError(
        "app.disableDomainBlockingFor3DAPIs() can only be called "
        "before app is ready");
    return;
  }
  content::GpuDataManagerImpl::GetInstance()
      ->DisableDomainBlockingFor3DAPIsForTesting();
}
bool App::IsAccessibilitySupportEnabled() {
  auto* ax_state = content::BrowserAccessibilityState::GetInstance();
  return ax_state->IsAccessibleBrowser();
}
void App::SetAccessibilitySupportEnabled(bool enabled) {