Since HackMD released its [beta API](https://hackmd.io/@hackmd-api/developer-portal/https%3A%2F%2Fhackmd.io%2F%40hackmd-api%2FrkoVeBXkq) several months ago, maybe we can provide an optional field for token, and using HackMD API if the token is given. If the token is not given, use the original way to fetch.
