Add new graph showing the average onion service descriptor count per directory
Mike asked me a while ago to make a graph showing the average onion service descriptor count per relay. This number could be extrapolated from the number of unique .onion addresses, the number of HSDir-flagged relays, and the information that each descriptor is stored on roughly six HSDir-flagged relays.
I made a sample graph that I'll attach to this ticket together with the code to make that graph.
Let's use this ticket to discuss whether such a graph would be useful to have on Tor Metrics, and if so, let's use it to write a useful description and work on a metrics-web patch.