docs(#3088): contributing index

Author: alex-courtis

CONTRIBUTING.md

@@ -18,9 +18,10 @@ markdown-toc --maxdepth=2 -i CONTRIBUTING.md
   * [check](#check)
 - [Diagnostics](#diagnostics)
 - [Backwards Compatibility](#backwards-compatibility)
-- [Documentation](#documentation)
-  * [Config And Mappings](#config-and-mappings)
-  * [API](#api)
+- [:help Documentation](#help-documentation)
+  * [Generated Content](#generated-content)
+  * [Updating And Generating](#updating-and-generating)
+  * [Checking And Linting](#checking-and-linting)
 - [Windows](#windows)
 - [Pull Request](#pull-request)
   * [Subject](#subject)