Add Marschner Hair Shading blogpost

Author: Alexander Gauggel

docs/_layouts/default.html

@@ -14,4 +14,4 @@
     </main>
   </body>
 
-</html>
+</html>

docs/_layouts/post.html

@@ -5,4 +5,18 @@
 <p>{{ page.date | date_to_string }} </p>
 <h1>{{ page.title }}</h1>
 
-{{ content }}
+{{ content }}
+
+<script>
+    window.MathJax = {
+        tex: {
+            tags: "ams"
+        }
+    };
+</script>
+<script
+    type="text/javascript"
+    id="MathJax-script"
+    async
+    src="https://cdn.jsdelivr.net/npm/mathjax@3/es5/tex-mml-chtml.js"
+></script>