Add a fetch polyfill with Promise

package.json

@@ -1,7 +1,7 @@
 {
   "name": "grapesjs",
   "description": "Free and Open Source Web Builder Framework",
-  "version": "0.9.24",
+  "version": "0.9.25",
   "author": "Artur Arseniev",
   "license": "BSD-3-Clause",
   "homepage": "http://grapesjs.com",
@@ -18,6 +18,7 @@
     "font-awesome": "^4.7.0",
     "jquery": "^3.1.1",
     "keymaster": "^1.6.2",
+    "promise-polyfill": "^6.0.2",
     "spectrum-colorpicker": "^1.8.0",
     "underscore": "^1.8.3"
   },

src/utils/fetch.js

@@ -0,0 +1,25 @@
+import Promise from 'promise-polyfill';
+
+window.Promise = window.Promise || Promise;
+
+export default typeof fetch == 'function' ? fetch.bind() : (url, options) => {
+  return new Promise((res, rej) => {
+    const req = new XMLHttpRequest();
+    req.open(options.method || 'get', url);
+    req.withCredentials = options.credentials == 'include';
+
+    for (let k in options.headers || {}) {
+      req.setRequestHeader(k, options.headers[k]);
+    }
+
+    req.onload = e => res(e.target.responseText, req);
+    req.onerror = rej;
+
+    // Actually, fetch doesn't support onProgress feature
+    if (req.upload && options.onProgress) {
+      req.upload.onprogress = options.onProgress;
+    }
+
+    req.send(options.body);
+  });
+}

yarn.lock

@@ -3985,6 +3985,10 @@ progress@^2.0.0:
   version "2.0.0"
   resolved "https://registry.yarnpkg.com/progress/-/progress-2.0.0.tgz#8a1be366bf8fc23db2bd23f10c6fe920b4389d1f"
 
+promise-polyfill@^6.0.2:
+  version "6.0.2"
+  resolved "https://registry.yarnpkg.com/promise-polyfill/-/promise-polyfill-6.0.2.tgz#d9c86d3dc4dc2df9016e88946defd69b49b41162"
+
 protocols@^1.1.0, protocols@^1.4.0:
   version "1.4.3"
   resolved "https://registry.yarnpkg.com/protocols/-/protocols-1.4.3.tgz#635b1c0785f0b389e8a012df1b1afffda9608b76"