Document the decision for rest over requests

There are two ways of using the GitHub REST API, the octokit.rest.* endpoint methods and octokit.request. Both act the same way, the octokit.rest.* methods are just added for convenience, they use octokit.request internally.

https://github.com/octokit/octokit.js#rest-api

With https://github.com/octokit/plugin-rest-endpoint-methods.js/ one can send all the request parameters as a single object, no matter if it's a route, query or body parameter