Support for additional API client configuration options

[ChrisHardie]

Feature request: it would be nice to support passing through additional configuration options to the underlying Automattic\WooCommerce\Client instance. For example, specifying a custom user agent.

Maybe it could be done via the config file or as an argument when constructing the API client? Here's the list of supported options: https://github.com/woocommerce/wc-api-php

Thanks for considering it.