lsteamclient: Synthesize SDK version 1.59x

[PeakKS]

CS2 uses UGC_STEAMUGC_INTERFACE_VERSION019 which was never included in a steamworks sdk release, so add it to a synthetic sdk version.

The workshop tools kinda sorta work now under proton. XWayland causes a bunch of awful flicker on the viewports. Winewayland fixes that, but in return context menus appear behind the 3d viewports :(. Also vrad3 crashes. Anyway it's better than nothing until we get the totally very real linux version of the workshop tools.