Add full-text search

Add a search box with a quick results popover, as well full results in
the sidebar on pressing enter.

app/controllers/search.js

@@ -0,0 +1,10 @@
+import Controller from '@ember/controller';
+
+export default class SearchController extends Controller {
+  queryParams = ['lat', 'lon', 'q', 'selected'];
+
+  lat = null;
+  lon = null;
+  q = null;
+  selected = null;
+}