docs: add news item and link release notes for 17.3.0

Signed-off-by: Emil Velikov <emil.velikov@collabora.com>
diff --git a/docs/relnotes.html b/docs/relnotes.html
index 98eb84f..d37094b 100644
--- a/docs/relnotes.html
+++ b/docs/relnotes.html
@@ -21,6 +21,7 @@
 </p>
 
 <ul>
+<li><a href="relnotes/17.3.0.html">17.3.0 release notes</a>
 <li><a href="relnotes/17.2.6.html">17.2.6 release notes</a>
 <li><a href="relnotes/17.2.5.html">17.2.5 release notes</a>
 <li><a href="relnotes/17.2.4.html">17.2.4 release notes</a>