scripts: move the steam game launch script to 'games'

This is because the script does not have anything specific to Proton
anymore or Wine for that matter, so we can use this as a handy tool to
open any games.

scripts/steam/launch.sh

@@ -1,11 +0,0 @@
-#!/bin/sh
-
-export MANGOHUD=1
-
-# https://docs.mesa3d.org/envvars.html
-export MESA_NO_DITHER=1         # Disables dither
-export MESA_BACK_BUFFER=pixmap  # For X only
-
-export DXVK_ASYNC=1
-
-gamemoderun "$@"