[Cashtab] Added support for AUD

Summary: Added support for Australian Dollar, related to task T2060. Resubmitting due to rebase error.

Test Plan:
cd web/cashtab && npm start
navigate to settings tab
select AUD from dropdown
navigate to wallet tab
ensure AUD is the selected currency & that conversion is taking place

Reviewers: bytesofman, #bitcoin_abc

Reviewed By: bytesofman, #bitcoin_abc

Differential Revision: https://reviews.bitcoinabc.org/D10627

Author: K-OC

web/cashtab/src/components/Common/Ticker.js

@@ -63,10 +63,12 @@ export const currency = {
             'hkd',
             'bhd',
             'sar',
+            'aud',
         ],
     },
     fiatCurrencies: {
         usd: { name: 'US Dollar', symbol: '$', slug: 'usd' },
+        aud: { name: 'Australian Dollar', symbol: '$', slug: 'aud' },
         bhd: { name: 'Bahraini Dinar', symbol: 'BD', slug: 'bhd' },
         brl: { name: 'Brazilian Real', symbol: 'R$', slug: 'brl' },
         gbp: { name: 'British Pound', symbol: '£', slug: 'gbp' },