Add sitemap CI/CD

Signed-off-by: Arija A. <ari@ari.lt>

sitemap.sh

@@ -0,0 +1,13 @@
+#!/bin/sh
+
+set -eu
+
+main() {
+    echo "<urlset>"
+    find pages/ -name '*.xhtml' | while read -r file; do
+        echo "<url><loc>https://purplebored.pl/${file}</loc><priority>1.0</priority></url>"
+    done
+    echo "</urlset>"
+}
+
+main >sitemap.xml