Change session template to have a link to attend

Author: polygonart6777

src/pretalx/agenda/templates/agenda/talk.html

@@ -87,6 +87,9 @@ <h3 class="talk-title">
                     <em>{{ phrases.agenda.schedule.do_not_record }}</em>
                 {% endif %}
             </small>
+            <button style="background-color: #2879c0;margin-top: 1em;">
+                <a href="https://seagl.org/attend" style="color: white;">Click here to attend the virtual conference</a>
+            </button>
         </h3>
         <div class="talk row">
             <div class="talk-content">