docs: update calendar, add news and link release notes to 17.3.9

Signed-off-by: Juan A. Suarez Romero <jasuarez@igalia.com>
diff --git a/docs/relnotes.html b/docs/relnotes.html
index 7de79b5..eb81b1a 100644
--- a/docs/relnotes.html
+++ b/docs/relnotes.html
@@ -21,6 +21,7 @@
 </p>
 
 <ul>
+<li><a href="relnotes/17.3.9.html">17.3.9 release notes</a>
 <li><a href="relnotes/17.3.8.html">17.3.8 release notes</a>
 <li><a href="relnotes/18.0.0.html">18.0.0 release notes</a>
 <li><a href="relnotes/17.3.7.html">17.3.7 release notes</a>