Add link to show only Unspent Outputs

I'd like a way to show only unspent outputs for a specified address. Same format as /address/:address but only unspents.

This is already available in the API (GET /address/:address/utxo) but GUI accessibility would be nice.

# Motivation

The [Glacier Protocol](https://glacierprotocol.org) requires users to manually select UTXOs for withdrawal, printing a QR code with the raw transaction data for each one. Today the process uses blockchain.info, but a few months ago that site removed their "Unspent Outputs" link from the GUI, so Glacier withdrawals are currently somewhat broken.

I can't find an alternative block explorer with similar functionality, but it seems like it would be easy to add to Blockstream.info.