Add missing static routes for favicon, about and acknowledgments

templates/about.html

@@ -0,0 +1,20 @@
+{% extends "base.html" %}
+
+{% block title %}About{% endblock title %}
+
+{%- block body %}
+<h1>About</h1>
+
+<p>en is a program to create a connected collection of texts.</p>
+
+<p>You define your graph using a plain-text configuration file and then en reads this file and generates a webpage like the one you are seeing right now.</p>
+
+<p>If you'd like to learn more:</p>
+
+<ul>
+    <li><a href="https://en.jutty.dev">Website</a></li>
+    <li><a href="https://en.jutty.dev/docs">Documentation</a></li>
+    <li><a href="https://codeberg.org/jutty/en">Source code repository</a></li>
+</ul>
+
+{%- endblock body %}