[token-server] Add database and initialize blacklist endpoints

Summary:
Add a database and initialize blacklist with usable API endpoints.

Going forward, will add a way to update the blacklist without updating the repo.

Test Plan:
npm test

ts-node index.ts and db is created and populated with blacklist
ctrl+c and shuts down gracefully
ts-node index.ts and db is connected, blacklist collection is not overwritten, we see console.log that it has 12 elements

Reviewers: #bitcoin_abc, emack

Reviewed By: #bitcoin_abc, emack

Differential Revision: https://reviews.bitcoinabc.org/D17020