feat: convert templates from njk to html

Note: Nunjucks will still process the templates, but this way they can
be plain HTML files and will be formatted properly.

src/_includes/partials/menu.html

@@ -0,0 +1,20 @@
+<nav aria-label="Main">
+  Menu.
+  <ul>
+    {% for item in navigation.top %}
+    <li>
+      <a
+        class="nav"
+        href="{{ item.url }}"
+        {{
+        helpers.getLinkActiveState(item.url,
+        page.url)
+        |
+        safe
+        }}
+        >{{ item.text }}</a
+      >
+    </li>
+    {% endfor %}
+  </ul>
+</nav>