Add and configure next.js sitemap generator

[elzannewentzel]

Stakeholders: Nick (DG), Fabiana, ROIDNA What: Implement the XML Sitemap optimisations specified in the audit feedback. Why: Several sitemaps submitted to GSC return a 404 status, and among the valid sitemaps, there is a relatively low proportion of valid URLs.

Assets:

• Audit document

Requirements:

• Add the next-sitemap package and configure it