Add gallery, about and error pages

site/templates/about.twig

@@ -0,0 +1,16 @@
+{% extends "base.twig" %}
+
+{% block main %}
+    <main>
+
+        <section class="about-section">
+
+            <article class="about">
+                <h2 class="about__title">{{ page.title }}</h2>
+                <div class="about__presentation">{{ page.text.kirbytext|raw }}</div>
+            </article>
+
+        </section>
+        
+    </main>
+{% endblock %}