Display a welcome video to new accounts

FIXME: we'll need a beter way, especially because this won't show up for
new users on busy accounts. To avoid seeing it blip everytime you
paginate it's set to `display: none` if there are enough events to
paginate. So people can scroll down to watch again if they only have a
few events.

app/assets/stylesheets/events.css

@@ -225,6 +225,17 @@
     text-align: center;
   }
 
+  .events__welcome-video {
+    .events:has(.day-timeline-pagination-link) + & {
+      display: none !important;
+    }
+
+    iframe {
+      aspect-ratio: 16 / 9;
+      inline-size: 100%;
+    }
+  }
+
   /* Event
   /* ------------------------------------------------------------------------ */
 

app/views/events/index.html.erb

@@ -24,3 +24,13 @@
     <%= day_timeline_pagination_link(@day_timeline, @filter) %>
   <% end %>
 <% end %>
+
+<div class="events__welcome-video flex justify-center">
+  <iframe
+      frameborder="0"
+      src="https://www.youtube.com/embed/rNKRdk7DLHM?si=IIjKjUIk5PchL0-a"
+      title="Fizzy Beta orientation"
+      allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture; web-share"
+      referrerpolicy="strict-origin-when-cross-origin"
+      allowfullscreen></iframe>
+</div>