2.8.1

This PR introduces beta accounting documentation generated from the Open API Spec.

The goal is to create simpler, more interactive docs for developers. Improving discoverability by having language specific endpoint examples.

https://xeroapi.github.io/xero-ruby/accounting/index.html

There are a few known misnomers, such as some cameCase variable names, so please report any issues so we can make this 100% accurate over time 🥳