add license notice

sass/_base.scss

@@ -110,3 +110,22 @@ pre {
 code {
   font-family: "Source Code VF";
 }
+
+#license {
+  margin: 0;
+  margin-left: auto;
+  float: right;
+  font-size: 12px;
+  max-width: 500px;
+}
+
+@media(max-width: 700px) {
+  #license {
+    float: left;
+    margin-top: 8px;
+  }
+}
+
+#license a {
+  margin: 0;
+}

templates/base.html

@@ -36,6 +36,9 @@
                     {% if config.extra.matrix_user %}
                         <a href="https://matrix.to/#/{{ config.extra.matrix_user }}">Matrix</a>
                     {% endif %}
+                    <p id="license">
+                        Except where otherwise noted, the content on this site is licensed under <a href="https://creativecommons.org/licenses/by-nc-sa/4.0/">CC BY-NC-SA 4.0</a>
+                    </p>
                 {% endblock footer %}
             </footer>
         </div>