Add Shopify metadata to ecommerce.js

dist/ecommerce.js

@@ -1,19 +1,16 @@
 //[ecommerce]
 // Uncomment the previous line for testing on webpagetest.org
 
-// README! Instructions for adding a new custom metric for the Web Almanac.
-//
-// 1. Refer for instructions for addding a custom metric in almanamc.js.
-// 2. This file has a special case where a custom metric uses 'fetch' and in that case we need to return a promise that resolves to JSON
-// 3. Test your change by following the instructions at https://github.com/HTTPArchive/almanac.httparchive.org/issues/33#issuecomment-502288773.
-// 4. Submit a PR to update this file.
-
 function fetchWithTimeout(url) {
   var controller = new AbortController();
   setTimeout(() => {controller.abort()}, 5000);
   return fetch(url, {signal: controller.signal});
 }
 
+function getShopifyMetadata() {
+  return window.Shopify;
+}
+
 return Promise.all([
   fetchWithTimeout('/.well-known/assetlinks.json').then(function(r) {
     if(!r.redirected && r.status === 200) {
@@ -30,7 +27,18 @@ return Promise.all([
     }
   })
 ]).then(([AndroidAppLinks, iOSUniveralLinks]) => {
-  return JSON.stringify({AndroidAppLinks, iOSUniveralLinks});
+  return {
+    AndroidAppLinks,
+    iOSUniveralLinks
+  };
 }).catch(error => {
-  return JSON.stringify({message: error.message, error: error});
+  return {
+    message: error.message,
+    error: error
+  };
+}).then(result => {
+  return {
+    ...result,
+    Shopify: getShopifyMetadata()
+  }
 });