[website] Add links to FAQ

Summary: Added Telegram and Discord links to the "how to get support" FAQ

Test Plan: visit e.cash/faq and scroll down to last question ("what's the best way to get technical support?")

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Subscribers: Fabien

Differential Revision: https://reviews.bitcoinabc.org/D15860