[FEAT]: Add support for Bitcoin as currency

[bumi]

Is your feature request related to a problem? Please describe.
Currently it is not possible to define prices in other currencies that the fixed list. Even though this is a ISO list it would be great to be able to charge users in Bitcoin (sats).

Describe the solution you'd like
Add Bitcoin to the list of supported languages. It can be added denominated in stats (the smallest unit in Bitcoin) which is commonly used. It would have zero decimal points and we can just use the current formatting settings.

Describe alternatives you've considered
Make the list dynamic and allow users to configure their own additional languages. But this would probably require some bigger change as the currencies are currently managed in the constant.

Additional context

I am happy to make a PR if you can point me to where to add it.

As by this comment the list of currencies is maintained here
but I have also seen there is a formatting configuration options: here

[bumi]

I've tried to add the currency, but I don't fully understand why I get different formattings on the invoice:

[jdenquin]

I assume we talked about it on our slack community also @bumi, whats the decision you made?