feat: Add "IESG" group at top of Groups menu (#9144)

* feat: Add "IESG" group at top of Groups menu
Creates an IESG group at the top of the Group dropdown menu that
points at https://datatracker.ietf.org/group/iesg/about/. Maybe
that value shouldn't be hardcoded into menu.html. This feature
is in response to issue #9018.

* feat: Add "IESG" group at top of Groups menu
This feature is in response to issue #9018. This commit is an
update to the original commit to add proper support for the
left menu and use a non-hardcoded URL for the IESG.

Author: Spectre17

ietf/templates/base/menu.html

@@ -19,6 +19,7 @@
             <span class="fw-bolder">Groups</span>
         </li>
     {% endif %}
+    <li><a class="dropdown-item" href="{% url "ietf.group.views.group_about" acronym="iesg" %}">IESG</a></li>
     {% if flavor == 'top' %}<li class="dropdown-header">By area/parent</li>{% endif %}
     {% wg_menu flavor %}
     <li class="dropend">