Add additional skiplink to bypass glossary nav (#242)

The normal skiplink skips the top level navigation, but the glossary
page also has its own sidebar inside the main element.

This commit adds a "skip to glossary content" skiplink, so users can
skip this as well.

templates/base/base.html

@@ -8,8 +8,10 @@
     <script>
       document.body.className += ' js-enabled' + ('noModule' in HTMLScriptElement.prototype ? ' govuk-frontend-supported' : '');
     </script>
+    {% block skiplinks %}
     <a href="#main-content" class="govuk-skip-link" data-module="govuk-skip-link">Skip to main content</a>
-
+    {% endblock %}
+
     {% include "base/navigation.html" %}
 
     <div class="govuk-width-container app-width-container">

templates/glossary.html

@@ -16,6 +16,7 @@ <h1 class="govuk-heading-l">Glossary</h1>
     </div>
     <div class="govuk-grid-row">
         <div class="govuk-grid-column-one-quarter" id="sticky-sidebar">
+            <a href="#glossary-content" class="govuk-skip-link" data-module="govuk-skip-link">Skip to glossary content</a>
             <ul class="govuk-list">
                 {% for parent_term in results %}
                     <li class="term-group">
@@ -32,7 +33,7 @@ <h1 class="govuk-heading-l">Glossary</h1>
                 {%endfor%}
             </ul>
         </div>
-        <div class="govuk-grid-column-three-quarters">
+        <div class="govuk-grid-column-three-quarters" id="glossary-content">
             {% for parent_term in results %}
                 <div class="term-group">
                     <h2 class="govuk-heading-l" id="{{ parent_term }}">{{ parent_term.name }}</h2>