add REST API to docs index

[steveburnett]

Description

https://github.com/prestodb/presto/tree/master/presto-docs/src/main/sphinx/rest has documentation pages for API resources that are not linked to in the Presto docs.

Added presto-docs/src/main/sphinx/rest.rst as an index page for REST API.
Added a line to presto-docs/src/main/sphinx/index.rst to include the new rest file.

Motivation and Context

The documentation for node, query, stage, statement and task should be accessible in the public docs without needing the direct URL for, for example, Node Resource.

This PR is in response to and hopefully fixes Issue #21157.

Impact

Documentation only.

Test Plan

Created a local build of the documentation.

• The new REST API heading appears in the left navbar of the Presto docs
• The REST API index page displays when it is selected in the left navbar
• The links to the individual pages in /rest/ work, both direct from the left navbar and within the REST API index page.

Contributor checklist

• Please make sure your submission complies with our development, formatting, commit message, and attribution guidelines.
• PR description addresses the issue accurately and concisely. If the change is non-trivial, a GitHub Issue is referenced.
• Documented new properties (with its default value), SQL syntax, functions, or other functionality.
• If release notes are required, they follow the release notes guidelines.
• Adequate tests were added if applicable.
• CI passed.

Release Notes

Please follow release notes guidelines and fill in the release notes below.

== RELEASE NOTES ==

General Changes
* Added links for the REST API resource pages to the Presto documentation.

[skairali]

LGTM

[steveburnett]

LGTM

Thanks for the review @skairali!

[agrawalreetika]

Thank you for fixing this @steveburnett. I can see the API docs in the index now.

[steveburnett]

Thank you for fixing this @steveburnett. I can see the API docs in the index now.

You're welcome! Thank you for noticing the problem and opening the issue.