Added crossorigin attribute to manifest link (#560)

The use-credentials value must be used when fetching a manifest that requires credentials, even if the file is from the same origin.

Author: petslane

src/index.html

@@ -26,7 +26,7 @@
     <meta name="apple-mobile-web-app-title" content="Node-RED">
     <meta name="mobile-web-app-capable" content="yes">
     <meta http-equiv="X-UA-Compatible" content="IE=edge">
-    <link rel="manifest" href="manifest.json">
+    <link rel="manifest" href="manifest.json" crossorigin="use-credentials">
     <link rel="icon" sizes="192x192" href="icon192x192.png">
     <link rel="shortcut icon" type="image/png" href="icon64x64.png">
     <link rel="apple-touch-icon" href="icon120x120.png">