Update PowerSelect and ember-concurrency

The previous versions were pulling in the old `@glimmer/component` v1 package which caused build errors.

Author: Windvis

app/controllers/index.js

@@ -36,12 +36,11 @@ export default class IndexController extends Controller {
     );
   }
 
-  @task(function* (term) {
-    yield timeout(250);
+  searchWerkingsgebied = task(async (term) => {
+    await timeout(250);
     let queryParams = { 'filter[naam]': term };
     return this.store.query('werkingsgebied', queryParams);
-  })
-  searchWerkingsgebied;
+  });
 
   flushQueryParams(step) {
     this.bestuursorgaanId = '';

app/templates/application.hbs

@@ -1,6 +1,7 @@
 {{page-title "Mandatendatabank Vlaanderen"}}
 
 <AuModalContainer />
+<BasicDropdownWormhole />
 
 <AuMainHeader @brandLink="https://mandaten.lokaalbestuur.vlaanderen.be/" @homeRoute="index" @appTitle="Mandatendatabank" @contactRoute="contact">
 </AuMainHeader>

ember-cli-build.js

@@ -4,6 +4,14 @@ const EmberApp = require('ember-cli/lib/broccoli/ember-app');
 
 module.exports = function (defaults) {
   const app = new EmberApp(defaults, {
+    babel: {
+      plugins: [
+        // ... any other plugins
+        require.resolve('ember-concurrency/async-arrow-task-transform'),
+
+        // NOTE: put any code coverage plugins last, after the transform.
+      ],
+    },
     '@embroider/macros': {
       setConfig: {
         '@appuniversum/ember-appuniversum': {