Fix iframe responsiveness

www/styles/structure.css

@@ -106,6 +106,10 @@ blockquote {
     width:100%;
     height:100%;
 }
+iframe.responsive {
+    width: 45rem;
+    height: 26rem;
+}
 .responsive-text {
     max-width: 45rem;
 }
@@ -118,3 +122,10 @@ blockquote {
     width: 20rem;
     height: 20rem;
 }
+
+@media(max-width: 45rem) {
+	iframe.responsive {
+    	width: 100%;
+    	height: 10rem;
+	}
+}