preload bg8.jpg

Former-commit-id: f93dea39
Former-commit-id: c91b2c20b161429cc24a3a11bc8dd014e00877e3 [formerly 63ac44ab929ed87af70cd9524a6f693e94bee39e]
Former-commit-id: 4ef1882d2e44ef7d8fb5398ce0bdf638b9882ffe

www/index.html

@@ -5,7 +5,7 @@
 	<title>World Soil Museum</title>
 
     <link rel="icon" type="image/x-icon" href="./assets/isric_icon.ico">
-    <link rel="prefetch" href="./images/background/bg5.jpg">
+    <link rel="preload" href="./images/background/bg5.jpg">
     <link rel="stylesheet" type="text/css"   href="https://fonts.googleapis.com/css?family=Asap">
 	<meta charset="utf-8" />
 	<meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1" />