Create new REST API index page
Problem to solve
Originally GitLab had a single API, the REST API. Over time we've added a GraphQL API and a SCIM API. Now we actually favor GraphQL over REST when implementing new features. However, the API documentation still heavily favors REST. For example, much of the documentation refers to the REST API but doesn't say so.
Proposal
Move "How to use the API" from the API index page to a new page: "How to use the REST API". Link to this page from the REST API section of the index page, and at the top of the REST API resources page.