Added real-time collection stats endpoint

In our most recent update, we've updated some of our documentation to reflect the current state of our API, including some exciting developments to our REST API that will help developers.

  • Added a new page for Retrieving collection stats
    • This endpoint will contain real-time statistics for floor prices, making interfacing your app with OpenSea much easier!
  • Added new page for Retrieving a single collection
    • Also contains real-time floor prices
  • Minor updates to the API reference including updating the model definitions pages for Assets, Events, Collections, and Accounts