docs: Add sha256 sums for the 10.3.1 release

Signed-off-by: Emil Velikov <emil.l.velikov@gmail.com>
(cherry picked from commit fa98c74692634de4f87694a40a299b59c4716ee5)
diff --git a/docs/relnotes/10.3.1.html b/docs/relnotes/10.3.1.html
index ea8e297..7de0506 100644
--- a/docs/relnotes/10.3.1.html
+++ b/docs/relnotes/10.3.1.html
@@ -30,7 +30,9 @@
 
 <h2>SHA256 checksums</h2>
 <pre>
-TBA
+155afcbad17be8bb80282c761b957d5cc716c14a1fa16c4f5ee04e76df729c6d  MesaLib-10.3.1.tar.gz
+b081d077d717e5d56f2d59677490856052c41573e50378ff86d6c72456714add  MesaLib-10.3.1.tar.bz2
+07a14febfed06412d519e091a62d24513fee6745f1a6f8a8f1956bfe04b77d15  MesaLib-10.3.1.zip
 </pre>
 
 <h2>New features</h2>