add Node.js fallback for file util

Check whether XMLHttpRequest is defined and if not use the Node.js built-in fetch method.

Author: PiotrNap

packages/mesh-common/src/utils/file.ts

@@ -1,6 +1,11 @@
-export function getFile(url: string) {
-  var Httpreq = new XMLHttpRequest();
-  Httpreq.open("GET", url, false);
-  Httpreq.send(null);
-  return Httpreq.responseText;
+export async function getFile(url: string) {
+  if (typeof XMLHttpRequest !== "undefined") {
+    var Httpreq = new XMLHttpRequest();
+    Httpreq.open("GET", url, false);
+    Httpreq.send(null);
+    return Httpreq.responseText;
+  } else {
+    const res = await fetch(url);
+    return res.text();
+  }
 }