Khatru Invite

A relay based on Khatru with a invite hierarchy feature.

some notes before running:

1. configure the relay settings in .env
2. manually add someone to the whitelist.json file, like this: [{"pk":"07adfda9c5adc80881bb2a5220f6e3181e0c043b90fa115c4f183464022968e6","invited_by":""}]