[Cashtab] Add support for ILS

Summary: Added support for Israeli Shekel. Related to task T2007.

Test Plan:
npm start
cd web/cashtab
navigate to configure page
select Philippine Peso in the Fiat Currency dropdown
ensure fiat is set to Israeli Shekel & that conversion is taking place

Reviewers: bytesofman, #bitcoin_abc

Reviewed By: bytesofman, #bitcoin_abc

Differential Revision: https://reviews.bitcoinabc.org/D10575