Move sitemap from html to njk to avoid typeerror on build

src/sitemap.njk

@@ -0,0 +1,16 @@
+---
+permalink: /sitemap.xml
+eleventyExcludeFromCollections: true
+---
+<?xml version="1.0" encoding="utf-8"?>
+<urlset xmlns="http://www.sitemaps.org/schemas/sitemap/0.9">
+    {% for page in collections.all %}
+       {% if not page.data.draft %}
+        <url>
+            <loc>{{ site.url }}{{ page.url | url }}</loc>
+            <lastmod>{{ page.date }}</lastmod>
+            <changefreq>{{page.data.changeFreq}}</changefreq>
+        </url>
+       {% endif %}
+    {% endfor %}
+</urlset>