add link to login page on registration page

accounts/templates/registration/registration_form.html

@@ -20,4 +20,10 @@
   </div>
 </div>
 
+<div class="row">
+  <div class="col-md-offset-4 col-md-4">
+    You already have an account? Please <a href="{% url 'login' %}">login</a>.
+  </div>
+</div>
+
 {% endblock %}