robots.txt points to an invalid sitemap.xml URL on data.gov

[tdlowden]

Google Lighthouse reports that our reference to /sitemap.xml in our robots.txt is invalid. Maybe it needs to be absolute rather than relative?

How to reproduce

1. Run Google Lighthouse report at https://pagespeed.web.dev/analysis/https-data-gov/egrvea4vmk?form_factor=desktop
2. View SEO issues

Expected behavior

The sitemap link is valid in robots.txt

Actual behavior

According to Lighthouse, the sitemap URL is invalid

Sketch

TBD

[neilmb]

Sitemap values in robots.txt need to be URLs, not just paths https://www.woorank.com/en/blog/how-to-locate-a-sitemap-in-a-robots-txt-file

This can be tricky in an 11ty site because when it builds the sitemap, it needs to know the base URL that the site will eventually be deployed on. https://github.com/cisagov/get.gov/pull/138/files is an example of a possible solution.

[neilmb]

https://github.com/18F/18f.gsa.gov/blob/e7b1b49c9d2156771c54632326f5fa587d622505/content/robots.txt#L5 is another solution?