[PLACEHOLDER] Support more historical relationship tracking

[JacobEvelyn]

This needs to be fleshed out much, much more, but the README states that friends is "a way to track the ebbs and flows of your relationships over time" and I think friends graph—the only real tool for doing this—is kind of weak in what it can tell you.

Ideally I want some sort of visualization (or this could be several visualizations) to show me things like: "You used to be very close with Grace Hopper but now you're much closer with Marie Curie," or "Watch how Marie Curie went from being a middling friend to your best friend."

I wonder if something around replaying history and computing where a friend's cumulative favorites ranking is each month and graphing that would be useful, or doing the same but showing month-by-month favorites rankings rather than cumulative?

Would love feedback @andypearson.