public bool IsReadOnly {get;}

//Pass in the full path to the style file on disk
public async Task<bool> IsReadOnly(string stylePath)
{
  //Add the style to the current project
  await QueuedTask.Run(() => StyleHelper.AddStyle(Project.Current, stylePath));
  StyleProjectItem style = Project.Current.GetItems<StyleProjectItem>().First(x => x.Path == stylePath);

  //returns true if style is read-only
  return style.IsReadOnly;
}