Add workaround for innerText in Jest

spec/frontend/test_setup.js

@@ -23,3 +23,12 @@ beforeEach(done => {
 });
 
 Vue.use(Translate);
+
+// workaround for JSDOM not supporting innerText
+// see https://github.com/jsdom/jsdom/issues/1245
+Object.defineProperty(global.Element.prototype, 'innerText', {
+  get() {
+    return this.textContent;
+  },
+  configurable: true, // make it so that it doesn't blow chunks on re-running tests with things like --watch
+});