Refactor to FastAPI

Created by: shiimizu

Feel free to accept or reject this PR

Changes/additions include:

• Switch to async
• FastAPI - the successor to Hug. You also get free docs and OpenAPI
• Use orjson for 4chan demo because orjson > ujson
• PostgreSQL (temporary workaround - only usable with a database that has Asagi schema as views)
• Switch to databases library
• Revert back to YAML
• Format code with black
• Various bugfixes