Add Responsive YT Video Embedding styling

The IBRACORP YouTube video embed was causing overflow scrolling horizontally on smaller screens/mobile devices.  Just tweaked some CSS to make the embed iframe responsive, which solves the horizontal overflow problem.

docs/_static/custom.css

@@ -187,4 +187,24 @@ a .logo-hover {
 }
 a:hover .logo-hover {
    display: block;
-}
+}
+/* Responsive YT Video Embedding */
+.responsiveYT {
+    position: relative;
+    height: 0;
+    padding-top: 56%;
+    overflow: hidden;
+    max-width: 100%;
+}
+.responsiveYT iframe,
+.responsiveYT object,
+.responsiveYT embed {
+    position: absolute;
+    top: 0;
+    left: 0;
+    width: 100%;
+    height: 100%;
+}
+.responsiveYT .fluid-vids {
+    position: initial !important
+}