**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
app_path_ = app_path;
}
base::FilePath App::GetPath(mate::Arguments* args, const std::string& name) {
  bool succeed = false;
  base::FilePath path;
  int key = GetPathConstant(name);
  if (key >= 0)
    succeed = base::PathService::Get(key, &path);
  if (!succeed)
    args->ThrowError("Failed to get '" + name + "' path");
  return path;
}
void App::SetPath(mate::Arguments* args,
                  const std::string& name,
                  const base::FilePath& path) {
  if (!path.IsAbsolute()) {
    args->ThrowError("Path must be absolute");
    return;
  }
  bool succeed = false;
  int key = GetPathConstant(name);
  if (key >= 0)
    succeed =
        base::PathService::OverrideAndCreateIfNeeded(key, path, true, false);
  if (!succeed)
    args->ThrowError("Failed to set path");
}
void App::SetDesktopName(const std::string& desktop_name) {