To enable 404 'age (#757)

docs/mkdocs.yml

@@ -8,6 +8,7 @@ theme:
     code: Lato Mono
   features:
     - navigation.top
+  custom_dir: overrides
 repo_url: https://github.com/johnkerl/miller
 repo_name: miller
 edit_uri: edit/master/main/docs/src

docs/overrides/404.html

@@ -0,0 +1,15 @@
+{% extends "main.html" %}
+
+<!-- Content -->
+{% block content %}
+<h1>404 - this page does not exists</h1>
+
+<p>Try searching for the content of your interest by browsing the sections of the site, or using the search form at the top right.</p>
+
+
+{% endblock %}
+
+
+
+<!-- Disqus integration -->
+{% block disqus %}{% endblock %}