Accessibility Updates to Super Rentals

The goal of this task is to take the updates made to the super rentals example in PR https://github.com/ember-learn/super-rentals/pull/121 and apply them to the tutorial

The following changes would be required:

- [ ] Add aria-hidden and tab-index -1 to location-map component to hide it from screen readers
- [ ] Add a label tag to the search input in list-filter.hbs
- [ ] Add alt text to rental image in rental-listing.hbs
- [ ] Install ember-a11y-testing addon and add config, as well as add auditing to test cases
- [ ] Fix link-to in https://guides.emberjs.com/release/tutorial/routes-and-templates/#toc_adding-a-banner-with-navigation