website: Added gem5 20.0.0.3 Doxygen

Change-Id: Ia1047e437fa5f9f2060c3d533ae9a86c2c31af39
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5-website/+/30974
Maintainer: Bobby R. Bruce <bbruce@ucdavis.edu>
Reviewed-by: Bobby R. Bruce <bbruce@ucdavis.edu>
Tested-by: Bobby R. Bruce <bbruce@ucdavis.edu>
diff --git a/_data/documentation.yml b/_data/documentation.yml
index d438fc9..55f5c8f 100755
--- a/_data/documentation.yml
+++ b/_data/documentation.yml
@@ -30,6 +30,8 @@
           url: http://doxygen.gem5.org/release/v20-0-0-0/index.html
         - page: v20.0.0.2
           url: http://doxygen.gem5.org/release/v20-0-0-2/index.html
+        - page: v20.0.0.3
+          url: http://doxygen.gem5.org/release/v20-0-0-3/index.html
 
     - title: gem5 Resources
       id: gem5_resources