added custom sitemap

sitemap.xml

@@ -0,0 +1,26 @@
+---
+layout: null
+---
+<?xml version="1.0" encoding="UTF-8"?>
+<urlset xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.sitemaps.org/schemas/sitemap/0.9 http://www.sitemaps.org/schemas/sitemap/0.9/sitemap.xsd" xmlns="http://www.sitemaps.org/schemas/sitemap/0.9">
+  {% for post in site.posts %}
+  <url>
+    <loc>{{ site.url }}{{ post.url }}</loc>
+    {% if post.lastmod == null %}
+    <lastmod>{{ post.date | date_to_xmlschema }}</lastmod>
+    {% else %}
+    <lastmod>{{ post.lastmod | date_to_xmlschema }}</lastmod>
+    {% endif %}
+    {% if post.sitemap.changefreq == null %}
+    <changefreq>weekly</changefreq>
+    {% else %}
+    <changefreq>{{ post.sitemap.changefreq }}</changefreq>
+    {% endif %}
+    {% if post.sitemap.priority == null %}
+    <priority>0.5</priority>
+    {% else %}
+    <priority>{{ post.sitemap.priority }}</priority>
+    {% endif %}
+  </url>
+  {% endfor %}
+</urlset>