A typeahead example that gets values from the `WikipediaService`

- remote data retrieval
- `debounceTime` operator
- `tap` operator
- `distinctUntilChanged` operator
- `switchMap` operator
- `catch` operator to display an error message in case of connectivity issue

Search for a wiki page:
@if (searching) { searching... } @if (searchFailed) {
Sorry, suggestions could not be loaded.
}

    Model: {{ model | json }}