[website] Add Huobi to list of BCHA-supporting exchanges

Summary: Received reports from multiple users that they have opened BCHA withdrawals.

Test Plan: Built and ran it locally, looked at page, checked link.

Reviewers: #bitcoin_abc, josephroyking

Reviewed By: #bitcoin_abc, josephroyking

Differential Revision: https://reviews.bitcoinabc.org/D9346