description update: performance numbers compared to gav1

OBS-URL: https://build.opensuse.org/package/show/multimedia:libs/dav1d?expand=0&rev=66

dav1d.spec

@@ -43,6 +43,8 @@ dav1d is a SIMD-enhanced decoder for AV1 video. It features
 
 AV1 is a royalty-free video codec by the Alliance for Open Media. It
 has the potential to be up to 20%% better than the HEVC codec.
+dav1d outperforms gav1 by about 20%% on ARM and 50%% on x86,
+and has better scaling properties for larger thread counts.
 
 %package        devel
 Summary:        Development files for %{name}