[graphics][gaming] Pre-install Steam bootstrap files for Steam Gamescope session

[LukeShortCloud]

trafficstars

It's possible to pre-install the Steam bootstrap files but the license and redistributability of this is unclear.

$ curl -Lo /usr/share/gamescope-session-plus/bootstrap_steam.tar.gz https://large-package-sources.nobaraproject.org/bootstrap_steam.tar.gz

https://github.com/ublue-os/bazzite/blob/v3.7.0/Containerfile#L808