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>
1 file changed