Add sitemap and fully automate article creation

Article pages now insert the cover images automatically & an excerpt is used instead of a description for the page description.

sitemap.xml

@@ -0,0 +1,25 @@
+---
+layout: none
+search: exclude
+---
+
+<?xml version="1.0" encoding="URF-8"?>
+<urlset xmlns="http://www.sitemaps.org/schemas/sitemap/0.9">
+    {% for page in site.pages %}
+    <url>
+        <loc>{{ page.url }}</loc>
+        <lastmod>{{ site.time | date: '%Y-%m-%d' }}</lastmod>
+        <changefreq>daily</changefreq>
+        <priority>0.5</priority>
+    </url>
+    {% endfor %}
+    
+    {% for post in site.posts %}
+    <url>
+        <loc>{{ post.url }}</loc>
+        <lastmod>{{ site.time | date: '%Y-%m-%d' }}</lastmod>
+        <changefreq>daily</changefreq>
+        <priority>0.5</priority>
+    </url>
+    {% endfor %}
+</urlset>