feat: fix copyright years

_includes/footer.html

@@ -12,7 +12,7 @@
         <ul class="contact-list">
           <li class="p-name">
             {% if site.attribution %}
-            2018 &copy; by <a href="{{ site.attribution-url }}">{{ site.attribution }}</a>
+            &copy; 2010-{{ site.time | date: '%Y' }} by <a href="{{ site.attribution-url }}">{{ site.attribution }}</a>
             {% else %}
               {{ site.title | escape }}
             {% endif %}