Add custom fields to Customers (Users) with REST API access

So WooCommerce adds some custom fields to each user such as billing address, etc, and this is accessible from the /customers API endpoint to READ/WRITE.

My question is, how do I go about adding some custom fields below billing/shipping address, lets say for example. Just simple text fields with specified keys and custom values. I also want to be able to edit these values via the REST API.