Add batch processing functions for fiat and satoshi conversions

[d4rp4t]

This PR introduces batch processing utilities to enhance the efficiency of fiat and satoshi conversions. By minimizing the number of API calls, these changes aim to optimize performance for scenarios involving multiple simultaneous conversions.

Changes in this PR:
Added batch processing functions:

• getBatchFiatValue: Calculates fiat values for an array of satoshis.
• getBatchSatoshiValue: Calculates satoshi values for an array of fiat amounts.
• getBatchFormattedFiatValue: Formats multiple fiat values as localized strings.

[rolznz]

@d4rp4t I am not sure this is really needed in this library as this is more custom and not necessarily required. The new methods you added can be done by the application, right?

[d4rp4t]

@d4rp4t I am not sure this is really needed in this library as this is more custom and not necessarily required. The new methods you added can be done by the application, right?

You're absolutely right, this can be implemented at the application level.
My main goal with this PR was to reduce unnecessary API calls, especially in scenarios like rendering lists or handling large datasets. By incorporating this functionality into the library, we can encourage a more efficient approach that helps prevent overloading the API.

[rolznz]

@d4rp4t on the other hand, by adding these methods we also complicate and increase the API surface and does not necessarily mean a user of the API would use them. I think this is a very specific use-case, so I still think this should be handled at the application level.