A new category called 'All Difficulties' has been added in the Misc. category tab. In this category you have to beat both difficulties in any order (probably starting with Hard and then Easy). Unlike regular games, all times are measured with real-time, though you can use the in-game times for reference. See the category rules for more details and feel free to ask if you have more questions.

The category is currently experimental, so it might get archived if there's not much interest in it, though there's already a few runs posted. In a few weeks I'll determine if it has enough traction in the community and then decide if we'll keep it. Good luck to those running this category.