Added the shell manage users page [ci skip]

app/templates/manage-users.html

@@ -0,0 +1,20 @@
+{% extends "admin_template.html" %}
+
+{% block page_title %}
+GOV.UK Notify | Manage users
+{% endblock %}
+
+{% block content %}
+
+<div class="grid-row">
+	<div class="column-two-thirds">
+		<h1 class="heading-xlarge">Manage users</h1>
+
+		<p>Here's where you can add or remove users of a service.</p>
+
+  	<p><a href="dashboard">Back to dashboard</a></p>
+
+	</div>
+</div>
+
+{% endblock %}