Fix docs (#796)

Follow up of https://github.com/elastic/docs/pull/701.

docs/authentication.asciidoc

@@ -1,3 +1,4 @@
+[[auth-reference]]
 == Authentication
 
 This document contains code snippets to show you how to connect to various Elasticsearch providers.

docs/breaking-changes.asciidoc

@@ -1,3 +1,4 @@
+[[breaking-changes]]
 == Breaking changes coming from the old client
 
 If you were already using the previous version of this client --i.e. the one you used to install with `npm install elasticsearch`-- you will encounter some breaking changes.

docs/child.asciidoc

@@ -1,3 +1,4 @@
+[[child-client]]
 == Creating a child client
 
 There are some use cases where you may need multiple instances of the client. You can easily do that by calling `new Client()` as many times as you need, but you will lose all the benefits of using one single client, such as the long living connections and the connection pool handling. +

docs/configuration.asciidoc

@@ -1,3 +1,4 @@
+[[client-configuration]]
 == Client configuration
 
 The client is designed to be easily configured as you see fit for your needs, following you can see all the possible basic options that you can use to configure it.

docs/extend.asciidoc

@@ -1,3 +1,4 @@
+[[extend-client]]
 == Extend the client
 
 Sometimes you need to reuse the same logic, or you want to build a custom API to allow you simplify your code. +

docs/introduction.asciidoc

@@ -1,3 +1,4 @@
+[[introduction]]
 == Introduction
 
 The official Node.js client for Elasticsearch.

docs/reference.asciidoc

@@ -1,3 +1,4 @@
+[[api-reference]]
 == API Reference
 
 ////////

docs/typescript.asciidoc

@@ -1,3 +1,4 @@
+[[typescript]]
 == TypeScript support
 
 The client offers a first-class support for TypeScript, since it ships the type definitions for every exposed API.

docs/usage.asciidoc

@@ -1,3 +1,4 @@
+[[client-usage]]
 == Usage
 
 Use the  client is pretty straightforward, it supports all the public APIs of Elasticsearch, and every method exposes the same signature.

scripts/utils/generateDocs.js

@@ -23,6 +23,7 @@ const dedent = require('dedent')
 
 function generateDocs (common, spec) {
   var doc = dedent`
+  [[api-reference]]
   == API Reference
 
   ////////
@@ -68,7 +69,7 @@ function commonParameters (spec) {
 
 function generateApiDoc (spec) {
   const name = Object.keys(spec)[0]
-  const documentationUrl = spec[name].documentation
+  const documentationUrl = fixLink(spec[name].documentation)
   const params = []
   // url params
   const urlParts = spec[name].url.parts
@@ -139,6 +140,17 @@ function generateApiDoc (spec) {
   return doc
 }
 
+// Fixes bad urls in the JSON spec
+function fixLink (str) {
+  if (!str) return ''
+  if (str.includes('/5.x/')) {
+    // fixes wrong url in ES5
+    str = str.replace(/5\.x/, '5.6')
+  }
+
+  return str
+}
+
 function getType (type, options) {
   switch (type) {
     case 'list':