Add patern for dynamic menu highlighting

Documents https://github.com/ebiwd/EBI-Framework/issues/136

content/websites/patterns/menu-auto-highlight/layout.html

+{{#markdown}}
+
+### Notes
+
+- The JS tries to automatically detect active menu item and append class `.active`.
+- It's currently used a bit of jQuery, but this could be coded as vanilla JS.
+- This pattern is likely of most help for JS-powered pages.
+{{/markdown}}
+
+{{> menu-auto-highlight}}

content/websites/patterns/menu-auto-highlight/menu-auto-highlight.html

+<header id="masthead" class="masthead">
+  <div class="masthead-inner row">
+    <!-- local-title -->
+    <div class="columns medium-12" id="local-title">
+      <h1><a href="../../" title="Back to [service-name] homepage">Detect active menu item</a></h1>
+    </div>
+    <!-- /local-title -->
+    <!-- local-nav -->
+    <nav>
+      <ul id="local-nav" class="dropdown menu float-left" data-description="navigational">
+        <li><a href="/">Current page (relative)</a></li>
+        <li><a href="/some-other-page">Not current page</a></li>
+      </ul>
+    </nav>
+    <!-- /local-nav -->
+  </div>
+</header>

content/websites/patterns/menu-auto-highlight/menu-auto-highlight.js

+// Currently this uses jQuery, but could be done without
+// Pull Requests welcome! :P
+function setNavigation() {
+  var path = window.location.pathname;
+  console.log('current path:', path)
+  path = path.replace(/\/$/, "");
+  path = decodeURIComponent(path);
+
+  $("#local-nav a").each(function () {
+    var href = $(this).attr('href');
+    if (path.substring(0, href.length) === href) {
+      $(this).closest('li').addClass('active');
+    }
+  });
+}
+
+$(function () {
+  // when jquery is ready...
+  setNavigation();
+});

content/websites/patterns/menu-auto-highlight/menu-auto-highlight.yml

+name: 'Detect and highlight active menu item'
+tags:
+  - navigation
+  - layout
+  - menus
+  - 'JS Framework'
+category: navigation
+description: Use this pattern to automatically highlight the current menu item depending on path.
+versions:
+  - 1.2.0
+  - 1.3.0
+author:
+  name: Ken Hawkins
+  github: khawkins98
+  twitter: khawkins98