Number formatting

[reneaaron]

• Seperate thousands by thin space (Unicode: U+2009 ( ,  )), If it's not easy in react, use normal space
• Add crossed zeroes to all numbers
• Decimals should work according to the chosen currency (I see comma as decimal for USD, which should be a dot)

[reneaaron]

There also seem to be some problems around the Intl bindings react native has. The option narrowSymbol doesn't seem to be available on all platforms:

https://github.com/getAlby/alby-mobile/blob/master/hooks/useGetFiatAmount.ts#L41

This makes e.g. USD display as US$ instead of just $.