Fix generation of sitemap.xml file (#4744)

mkdocs.yml

@@ -1,7 +1,9 @@
 site_name: NGINX Ingress Controller
 strict: true
 repo_name: "kubernetes/ingress-nginx"
-repo_url: "https://github.com/kubernetes/ingress-nginx"
+repo_url: https://github.com/kubernetes/ingress-nginx
+site_url: https://kubernetes.github.io/ingress-nginx
+
 markdown_extensions:
   - admonition
   - codehilite
@@ -11,6 +13,8 @@ markdown_extensions:
   - pymdownx.superfences
   - toc:
       permalink: true
+  - meta
+
 theme:
   name: material
   feature: