docs: Add sha256sums for the 10.5.9 release

Signed-off-by: Emil Velikov <emil.l.velikov@gmail.com>
diff --git a/docs/relnotes/10.5.9.html b/docs/relnotes/10.5.9.html
index dd71fed..a1d11c3 100644
--- a/docs/relnotes/10.5.9.html
+++ b/docs/relnotes/10.5.9.html
@@ -31,7 +31,8 @@
 
 <h2>SHA256 checksums</h2>
 <pre>
-TBD
+0c081b59572ee9732e7438d34adc3817fe8cc8d4b58abc0e71fd4b4c904945cb  mesa-10.5.9.tar.gz
+71c69f31d3dbc35cfa79950e58a01d27030378d8c7ef1259a0b31d4d0487f4ec  mesa-10.5.9.tar.xz
 </pre>