docs: add sha256 checksums for 17.2.8

Signed-off-by: Andres Gomez <agomez@igalia.com>
diff --git a/docs/relnotes/17.2.8.html b/docs/relnotes/17.2.8.html
index a209b35..6e53285 100644
--- a/docs/relnotes/17.2.8.html
+++ b/docs/relnotes/17.2.8.html
@@ -31,7 +31,8 @@
 
 <h2>SHA256 checksums</h2>
 <pre>
-TBD
+c715c3a3d6fe26a69c096f573ec416e038a548f0405e3befedd5136517527a84  mesa-17.2.8.tar.gz
+6e940345cceaadfd805d701ed2b956589fa77fe8c39991da30ed51ea6b9d095f  mesa-17.2.8.tar.xz
 </pre>