Add alias for CNH currency

[nixstrom]

Context

The currency of PRC (Renminbi) has two different currency codes - one for mainland China (CNY) and one for offshore banking (CNH). The latter does not have a flag, even if it is an active currency.

Changes

I propose simply adding a CSS selector to point this currency code to the regular PRC flag.

Checklist

• [ ] I have considered the impact of this change and added a Change Classification Label (change:standard, change:impactful, change:emergency)
• [ ] Change meets or does not compromise the Baseline Security Requirements

[nixstrom]

This PR closes #47

[azrulamir]

Is this going to be merged?

[nixstrom]

I have since quit my job, so I actually no longer need it.

I would be happy to update this PR, but it doesn't look like there is any motivation from the Transferwise team to accept it, so I'm afraid it would be a wasted effort.