Added responsive banner

index.html

@@ -26,7 +26,11 @@
         </div>
       </div>
       <div class="banner">
-        <img src="images/celticinfo_banner.png" alt="CelticInfo">
+        <picture>
+          <source media="(min-width: 1582px)" srcset="images/celticinfo_banner_large.png">
+          <source media="(min-width: 769px)" srcset="images/celticinfo_banner.png">
+          <img src="images/celticinfo_banner_small.png" alt="CelticInfo">
+        </picture>        
       </div>
       <div class="footer">
         <div class="footer-left">