test: test_questions_ui_extras: add tests for UI extras (!1911)

Ensure that it does not fail with the "none" UI (it does at the moment).

test/testdata/init_questions_device/aports/main/postmarketos-ui-weston/APKBUILD

@@ -5,7 +5,12 @@ pkgdesc="(Wayland) Reference compositor (demo, not a phone interface)"
 url="https://postmarketos.org"
 arch="noarch"
 license="GPL-3.0-or-later"
+subpackages="$pkgname-extras"
 
 package() {
         mkdir "$pkgdir"
 }
+
+extras() {
+        pkgdesc="Super cool extras you will definitely (not?) need"
+}