Fix favicon on non-home pages.

docs/_includes/layouts/base.njk

@@ -4,7 +4,7 @@
 		<meta charset="utf-8">
 		<meta name="viewport" content="width=device-width, initial-scale=1.0">
                 <meta name="generator" content="{{ eleventy.generator }}">
-		<link rel="icon" href="docs/static/borgmatic.png" type="image/x-icon">
+		<link rel="icon" href="https://torsion.org/borgmatic/docs/static/borgmatic.png" type="image/x-icon">
 		<title>{{ subtitle + ' - ' if subtitle}}{{ title }}</title>
 {%- set css %}
 {% include 'index.css' %}