Add failing test for missing data of FastBoot's package.json

Adds accessing `request.host` to `fastboot-app` that reproduces the missing FastBoot package.json data (here `hostWhitelist`) reported in embroider-build#160.

test-packages/fastboot-app/app/routes/index.js

@@ -0,0 +1,14 @@
+import Route from '@ember/routing/route';
+import { inject as service } from '@ember/service';
+
+export default class IndexRoute extends Route {
+  @service
+  fastboot;
+
+  beforeModel() {
+    // This is only to to make sure we can correctly access the request's host, which fails if FastBoot's `hostWhitelist`
+    // is not correctly set up. This is the case when the changes added to /dist/package.json by FastBoot are not correctly
+    // merged by Embroider. So this serves as a reproduction of https://github.com/embroider-build/embroider/issues/160
+    return this.fastboot.isFastBoot ? this.fastboot.request.host : null;
+  }
+}