Revamp docs to highlight use cases and explain EMU attribution flow

[ahpook]

Is your feature request related to a problem?

Right now the README in the repo dives right into how to develop the app - this is probably too much detail for the casual browser 😸

Describe the solution you'd like

The front page should probably just highlight the problem statement and show how the app works from a user perspective (maybe embed a demo video?). The how-to-develop info that's there now is all super helpful for devs but can probably move into its own file in the docs/ subdirectory.

Describe alternatives you've considered

No response

Additional context

No response

[ahpook]

Specifically lots of people are confused about the attribution flow for contributions that start off with an EMU user and then flow upstream to that user's public identity.