[website] Update exchanges list for BCHA page

Summary:
Remove exchanges that don't have BCHA deposits and withdrawals enabled, and add ones that do.
List of exchanges provided by @Phlip based on user reports.

Test Plan:
Built and ran the site locally, tested links and looked through exchanges.
Legitimacy of exchanges is based on reports from users.

Reviewers: #bitcoin_abc, josephroyking

Reviewed By: #bitcoin_abc, josephroyking

Differential Revision: https://reviews.bitcoinabc.org/D9223