[www] Update copyright years in footer

It's not 2019 any more (I wouldn't mind it, though).

Dynamically update the copyright year to include the current year
("2019" becomes "2019 - 2020").

Signed-off-by: Philipp Wagner <phw@lowrisc.org>
diff --git a/site/landing/layouts/index.html b/site/landing/layouts/index.html
index 6ab336b..0baf1d1 100644
--- a/site/landing/layouts/index.html
+++ b/site/landing/layouts/index.html
@@ -325,7 +325,7 @@
       </ul>
     </nav>
 
-    <p>© 2019 lowRISC contributors, <a href="/privacy-policy/">Privacy
+    <p>© 2019 &ndash; {{ now.Format "2006" }} lowRISC contributors, <a href="/privacy-policy/">Privacy
       Policy</a>, <a href="/usage-policy/">Usage Policy</a>.</p>
     <p>The text content on this website is licensed under a
     <a href="https://creativecommons.org/licenses/by-sa/4.0/">Creative Commons