add cloning instructions to the bottom of articles

templates/article.html

@@ -8,4 +8,15 @@
 
 {{ page.content | safe }}
 
+<details>
+    <summary>Get a copy of this Library</summary>
+    <h4>Using <code>git</code></h4>
+    <pre>
+git clone https://tildegit.org/southlondon/library.git</pre>
+    <h4>Using <code>wget</code></h4>
+    <pre>
+wget https://tildegit.org/southlondon/library/archive/main.zip
+unzip main.zip</pre>
+</details>
+
 {% endblock content %}