making an accessible skip to content button for users who are using the tab...

making an accessible skip to content button for users who are using the tab button to go through the page

plugins/CoreHome/templates/_topScreen.twig

 <div id="header">
+    <a href='#main' tabindex="0" class="accessibility-skip-to-content">{{'SkipToContent'|translate}}</a>
     {% include "@CoreHome/_logo.twig" %}
-<a href='#main' tabindex="0" class="accessibility-skip-to-content">Skip to content</a>
     {% include "@CoreHome/_topBar.twig" %}
 </div>