Here is an example commit of what needs to be done to add another currency option:
https://github.com/discourse/discourse-subscriptions/commit/d63f241e0d703afafbea3eb977e708275085dc12
Just adding it here to document it, so that we have something to follow for the next currency option we need to add.
I’ll work on adding the CHF currency for you @Isambard.
If someone else would like more currency options added please comment below.