Nuxt 2.13.0 compatibility (nuxt static export)

### What problem does this feature solve?

It would be nice if the sitemap automatically generate routes in combination with the Nuxt `static` option 


<div align="right"><sub><em>This feature request is available on <a href="https://cmty.app/nuxt">Nuxt</a> community (<a href="https://cmty.app/nuxt/sitemap-module/issues/c106">#c106</a>)</em></sub></div>