Merge pull request #45855 from pstn/steam-python3

steam: Add python3 to runtime for steam play / proton

Changed files
+2
pkgs
games
+2
pkgs/games/steam/chrootenv.nix
···
# Open URLs
xdg_utils
iana-etc
+
# Steam Play / Proton
+
python3
] ++ lib.optional withJava jdk
++ lib.optional withPrimus primus
++ extraPkgs pkgs;