changed dir structure to handle second version of the book

Vanilla/templates/admin/index.html.php

@@ -0,0 +1,10 @@
+<?php include dirname(path: __DIR__) . '/_header.html.php'; ?>
+
+<br>
+<h1>Address Book - Admin</h1>
+<a href="<?= $router->path('app_admin_users'); ?>">&#128113;&nbsp;Users</a>
+
+<?php include dirname(path: __DIR__) . '/_footer.html.php' ?>
+
+<button type="button" class="info_button" id="info_button" onclick="setInfo('Test Info - auto hide')">Info</button>
+<button type="button" class="error_button" onclick="setError('Test Error - must be closed manually')">Error</button>