Update sitemap for CRDL

Thoughts:

• Confirmed last time I did this that NOT having URLs in the sitemap (like every record) will not prevent Google from indexing all the records.
• There is a limit on the number of URLs in a sitemap: 50,000 (see here)
• Should probably submit the sitemap to Google Search console.
• Should set up the rake task to run periodically
• Should add the URL of the sitemap index file to public/robots.txt to help search engines find the sitemap. The URL should be the complete URL to the sitemap index. For example:
  • Sitemap: http://www.example.com/sitemap.xml.gz

Other resources:

• https://www.jack-reed.com/2020/01/10/sitemaps-that-scale.html
• https://vufind.org/wiki/administration:search_engine_optimization