style: widen layout max-width to 1400px

Author: prabha-git

docs/stylesheets/extra.css

@@ -27,4 +27,9 @@ code {
     margin-top: -1em;
     margin-bottom: 1.5em;
     font-style: italic;
+}
+
+/* Widen the layout */
+.md-grid {
+    max-width: 1400px;
 }