**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
const std::string& info_type) {
  auto* const gpu_data_manager = content::GpuDataManagerImpl::GetInstance();
  scoped_refptr<util::Promise> promise = new util::Promise(isolate);
  if (info_type != "basic" && info_type != "complete") {
    promise->RejectWithErrorMessage(
        "Invalid info type. Use 'basic' or 'complete'");
    return promise->GetHandle();
  }
  std::string reason;
  if (!gpu_data_manager->GpuAccessAllowed(&reason)) {
    promise->RejectWithErrorMessage("GPU access not allowed. Reason: " +
                                    reason);
    return promise->GetHandle();
  }
  auto* const info_mgr = GPUInfoManager::GetInstance();
  if (info_type == "complete") {
#if defined(OS_WIN) || defined(OS_MACOSX)
    info_mgr->FetchCompleteInfo(promise);
#else
    info_mgr->FetchBasicInfo(promise);
#endif
  } else  {
    info_mgr->FetchBasicInfo(promise);
  }
  return promise->GetHandle();
}
static void RemoveNoSandboxSwitch(base::CommandLine* command_line) {