Provide accessibility improvement for search results

Acceptance criteria checks out. I am getting a PHP warning:

Warning: Undefined array key "results_accessibility" in Drupal\google_cse\Plugin\Search\GoogleSearch->buildResults() (line 432 of /app/web/modules/contrib/google_cse/src/Plugin/Search/GoogleSearch.php)

Also, should the H3 contain a div element?

Also, looks like I can't uncheck the "Add accessibility improvements to search results" checkbox.

Thanks for the review, @mmarler! I've resolved the two things noted in comment #9 with the latest commits in #11. As for the comment in #10:

Also, looks like I can't uncheck the "Add accessibility improvements to search results" checkbox.

The setting is designed only to be available when the previous setting, "Display search results," is set to "On this site (requires JavaScript)". Is that possibly the issue -- the configuration is set to "On Google"?

The search results are now displaying 2 search result titles. Looks like there are 2 .gs-title classes being found and displayed.

I can uncheck the "Add accessibility improvements to search results" checkbox and save the form. But when I revisit the page it's checked again. Looks like the default config is set to TRUE:

'#default_value' => $this->configuration['results_accessibility'] ?? $default['results_accessibility'],

Note that commit https://git.drupalcode.org/project/google_cse/-/merge_requests/16/diffs?... also revises the business logic so that existing sites will automatically inherit the accessibility tweaks without having to update the configuration, but can also opt out of this if desired by the UI configuration.

Looks good. Setting to RTBC.