Update hux-blog.less

Author: TwperBody

less/hux-blog.less

@@ -531,6 +531,7 @@ samp {
   background-color: @brand-gray;
   background-attachment: scroll;
   .background-cover;
+  background-size: cover;
   // NOTE: Background images are set within the HTML using inline CSS!
   margin-bottom: 0px; /* 0 on mobile, modify by Hux */
   @media only screen and (min-width: 768px) {