Add AnchorJS logic for header links (#10155)

* Add AnchorJS JavaScript

* Remove existing inpage_heading logic

* Remove underline from anchor tags

* Use single icon and add touch visibility

* Use paragraph link icon for AnchorJS

* Update Sass to use code formatting in docsContent headers

* Update header size coverage to H3-H6

layouts/partials/head.html

@@ -27,6 +27,7 @@
 <meta property="og:image" content="{{ index . 0 | replaceRE ".*src=\"(.+?)\".*" "$1" }}" />
 {{ end }}
 {{ end }}
+<script src="{{ "js/anchor-4.1.1.min.js" | relURL }}"></script>
 <script src="{{ "js/jquery-3.2.1.min.js" | relURL }}"></script>
 <script src="{{ "js/jquery-ui-1.12.1.min.js" | relURL }}"></script>
 <script src="{{ "js/bootstrap-3.3.7.min.js" | relURL }}"></script>