Switch appendFilesToHead to use template strings to make it clearer

autoHeightWebView/index.android.js

     if (!files) {
       return script;
     }
-    for (let file of files) {
-      script =
-        `
-                var link  = document.createElement('link');
-                link.rel  = '` +
-        file.rel +
-        `';
-                link.type = '` +
-        file.type +
-        `';
-                link.href = '` +
-        file.href +
-        `';
-                document.head.appendChild(link);
-                ` +
-        script;
-    }
-    return script;
+    return files.reduceRight((file, combinedScript) => `
+      var link  = document.createElement('link');
+      link.rel  = '${file.rel}';
+      link.type = '${file.type}';
+      link.href = '${file.href}';
+      document.head.appendChild(link);
+      ${combinedScript}
+    `, script)
   }
 
   appendStylesToHead(styles, script) {

autoHeightWebView/index.ios.js

         if (!files) {
             return script;
         }
-        for (let file of files) {
-            script =
-                `
-                var link  = document.createElement('link');
-                link.rel  = '` + file.rel + `';
-                link.type = '` + file.type + `';
-                link.href = '` + file.href + `';
-                document.head.appendChild(link);
-                `+ script;
-        }
-        return script;
+        return files.reduceRight((file, combinedScript) => `
+          var link  = document.createElement('link');
+          link.rel  = '${file.rel}';
+          link.type = '${file.type}';
+          link.href = '${file.href}';
+          document.head.appendChild(link);
+          ${combinedScript}
+        `, script)
     }
 
     appendStylesToHead(styles, script) {