[Cashtab] Support Bahraini Dinar

Summary: Add support for Bahraini Dinar. Related to task T2035

Test Plan:
cd web/cashtab
npm start
navigate to settings tab
set currency as Bahraini Dinar
navigate to wallet tab
ensure currency is set to Bahraini Dinar and conversion is taking place.

Reviewers: bytesofman, #bitcoin_abc

Reviewed By: bytesofman, #bitcoin_abc

Differential Revision: https://reviews.bitcoinabc.org/D10600