[REF] qweb: split code into 3 files

closes #84

src/utils.ts

@@ -156,3 +156,12 @@ export function whenReady(fn) {
     document.addEventListener("DOMContentLoaded", fn, false);
   }
 }
+
+export function parseXML(xml: string): Document {
+  const parser = new DOMParser();
+  const doc = parser.parseFromString(xml, "text/xml");
+  if (doc.getElementsByTagName("parsererror").length) {
+    throw new Error("Invalid XML in template");
+  }
+  return doc;
+}