Determine if utxo is colored on client side

[cgcardona]

Description

Currently when calling REST's address/utxo it will return all utxo and the client needs to determine if any of the utxo are colored for SLP tokens.

Ex: https://rest.bitcoin.com/v2/address/utxo/simpleledger:qzht6wanjrxqjp6qyla6t856mfhgktg3wcphvqpm6m

You could use isTokenUtxo but that would require an extra network call for each utxo.

1. We need to make a batch endpoint for that method.
2. We need a method for decoding OP_RETURN on the client and checking if it's slp.

Does this already exist in slpjs? If so expose it in SLP SDK and add docs.