Search: move indexing from the legacy docsearch-scraper to the Algolia Crawler #34

Follow-up of #25 (item 5, DocSearch migration).

#33 moves the site search front end to @docsearch/js 3.9.0 on the existing index doc_openidentityplatform. The index is still written by the legacy docsearch-scraper (algolia/docsearch-scraper:v1.12.0, no longer maintained), which the "Reindex docs" step of .github/workflows/publish.yml runs with docsearch/config.json after every deployment.

The replacement is the Algolia Crawler. #33 adds docsearch/crawler-config.js — the same crawl (pages, exclusions, selectors), writing a new index doc_openidentityplatform_v3 — but it has not been run: it needs Crawler access on the Algolia application X0ME9NKL6F, which an open-source documentation site gets through the DocSearch program.

Steps (also in docsearch/readme.md)

1. Get Crawler access for the application X0ME9NKL6F (or apply to the DocSearch program).
2. Create a crawler in the Crawler dashboard from docsearch/crawler-config.js; the dashboard sets the API key.
3. Run it into doc_openidentityplatform_v3 and check the results (e.g. a local build with that indexName in supplemental-ui/partials/footer-scripts.hbs); schedule it, or trigger it after each deployment.
4. In one pull request: switch indexName to doc_openidentityplatform_v3, remove the "Reindex docs" step from publish.yml and docsearch/config.json. The ALGOLIA_API_KEY secret (write key of the legacy scraper) can then be removed.