@tatsumoto I already added a link to your add-on on top of the ankiweb listing of my add-on. I don’t plan to invest much into adjusting my add-on to future anki changes so I’ll probably remove it one day - at the moment I keep it because my source code is very short and I use it myself.
Right hand reviews / hjkl answer shortcuts / Handy Answer Keys (configurable) [Official thread]
Cool! By the way, your add-on should be working in 2.1.64 (and newer).