[website] Update BCHA and Bitcoin Cash statements on homepage.
Bitcoin Cash info was out-of-date, and BCHA info was missing.
Also update donation info to include both currencies.
Built and ran locally
Read over page and make sure it conveys the right message.
Reviewers: deadalnix, jasonbcox, #bitcoin_abc
Reviewed By: deadalnix, #bitcoin_abc
Differential Revision: https://reviews.bitcoinabc.org/D8528