Maintain aspect ratio even when JS is disabled

assets/css/default.css

@@ -201,3 +201,16 @@ div {
   background-size: cover;
   object-fit: cover;
 }
+
+#player {
+  position: absolute;
+  left: 0;
+  top: 0;
+  height: 100%;
+}
+
+#player-container {
+  position: relative;
+  padding-bottom: 56.25%;
+  height: 0;
+}

src/invidious/views/watch.ecr

@@ -26,7 +26,7 @@
 <title><%= HTML.escape(video.title) %> - Invidious</title>
 <% end %>
 
-<div class="h-box">
+<div id="player-container" class="h-box">
   <%= rendered "components/player" %>
 </div>