Fetch initial io.search results asynchronously if not given

This changes behavior in that an empty search bar is never shown
anymore, we will immediately fetch data when the input renders.

Closes T-605

src/examples/basic/index.ts

@@ -406,6 +406,7 @@ const interval = new Interval({
           const [r1, r2] = await io.group([
             io.search('One', {
               onSearch: async query => fakeDb.find(query),
+              initialResults: await fakeDb.find('jo'),
               renderResult: result => ({
                 label: `${result.first_name} ${result.last_name}`,
               }),