[website] Update FAQ with BEP-20 token info

Summary: Now that Binance has created a BEP-20 XEC token,we should give users some info about it.

Test Plan:
Read the info, and make sure it's the message we want to send.
Built the page and tested the link.

Reviewers: bytesofman, #bitcoin_abc

Reviewed By: bytesofman, #bitcoin_abc

Maniphest Tasks: T1880

Differential Revision: https://reviews.bitcoinabc.org/D10273