Feat Request: add bitcoin as selectable currency

[coleEthomas]

Is your feature request related to a problem? Please describe.
My request is not related to a problem as all the currency options I have tested work as intended.

Describe the solution you'd like
I would like an option to see my cluster's cost breakdown in bitcoin

[mattray]

Feel free to submit a patch to https://github.com/opencost/opencost/blob/develop/ui/src/constants/currencyCodes.js