JS Indexing Updates and Alert Banner Styling

[amanifarooque]

Summary

• updated the alert banner to use for feature announcements
• added references to JS indexing wherever we discuss search.gov indexing workflows
• updated hint that appears in the admin center

PR Checklist

• [x] Test Cloud.gov Pages preview link for your branch for functionality - make sure all links and buttons work, javascript works as intended, and updates display as expected
• [x] Conduct a HemingwayApp review of the content for plain language. Request plain language review in #helpwanted if needed before merging this PR
• [x] Conduct a Lighthouse Audit via Chrome Developer Tools. Identify any issues that must be addressed before merging, and fix
• [x] Ensure no non-public information is published in the commit messages

[amanifarooque]

Home Page: https://cg-a72b65a7-73f0-4859-a1d7-dc953cf6ade8.app.cloud.gov/preview/gsa/search-gov-website/js-indexing-updates/

What we index: https://cg-a72b65a7-73f0-4859-a1d7-dc953cf6ade8.app.cloud.gov/preview/gsa/search-gov-website/js-indexing-updates/indexing/what-searchgov-indexes.html#js-indexing

indexing workflow: https://cg-a72b65a7-73f0-4859-a1d7-dc953cf6ade8.app.cloud.gov/preview/gsa/search-gov-website/js-indexing-updates/indexing/indexing-workflow.html

site launch guide: https://cg-a72b65a7-73f0-4859-a1d7-dc953cf6ade8.app.cloud.gov/preview/gsa/search-gov-website/js-indexing-updates/get-started/site-launch-guide.html#select-index

I also updated the hints.yml file.