docs: override sitemap.xml to only include latest results

This PR overrides the sitemap to only include, for example, v1.0 results
if that's our specified latest version. This should fix Google's
indexing of our docs to only include the latest results.

Signed-off-by: Spencer Smith <spencer.smith@talos-systems.com>

website/layouts/sitemap.xml

@@ -0,0 +1,12 @@
+{{ printf "<?xml version=\"1.0\" encoding=\"utf-8\" standalone=\"yes\"?>" | safeHTML }}
+<urlset xmlns="http://www.sitemaps.org/schemas/sitemap/0.9" xmlns:xhtml="http://www.w3.org/1999/xhtml">
+  {{- range .Data.Pages -}}{{ $currentVersion := index (split .Permalink "/" ) 1 }}{{ $currentVersionDir := $currentVersion | printf "/%s"}}{{ if and .Permalink (ne .Params.sitemap_exclude true) (eq $currentVersionDir site.Params.url_latest_version)}}
+  <url>
+    <loc>https://talos.dev{{ .Permalink }}</loc>{{ if not .Lastmod.IsZero }}
+    <lastmod>{{ safeHTML (.Lastmod.Format "2006-01-02T15:04:05-07:00") }}</lastmod>{{ end }}{{ with .Sitemap.ChangeFreq }}
+    <changefreq>{{ . }}</changefreq>{{ end }}{{ if ge .Sitemap.Priority 0.0 }}
+    <priority>{{ .Sitemap.Priority }}</priority>{{ end }}{{ if .IsTranslated }}{{ range .Translations }}
+    <xhtml:link rel="alternate" hreflang="{{ .Language.Lang }}" href="{{ .Permalink }}"/>{{ end }}
+    <xhtml:link rel="alternate" hreflang="{{ .Language.Lang }}" href="{{ .Permalink }}"/>{{ end }}
+  </url>{{ end }}{{ end }}
+</urlset>