About Page: Add release video and update post embed.

Props camikaos, siobhan, rosso99, wonderboymusic.
See #34663.

git-svn-id: https://develop.svn.wordpress.org/trunk@35839 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-admin/css/about.css

@@ -181,7 +181,7 @@
 /* 2.1 - Typography */
 
 .about-wrap .headline-feature h2 {
-	margin: 50px 0 30px;
+	margin: 30px 0 30px;
 	font-size: 2.2em;
 	font-weight: 300;
 	line-height: 1.3;
@@ -226,11 +226,12 @@
 
 /* 2.2 - Structure */
 
-.about-wrap .feature-video {
+.about-wrap .headline-feature.feature-video {
 	position: relative;
 	margin: 40px 0;
-	padding-bottom: 56.25%; /* video is 1280 x 720 */
+	padding-bottom: 56.25%;
 	width: 100%;
+	max-width: 100%;
 	height: 0;
 	text-align: center;
 }