Slippery slopes! — Climbey Steam update #398461

Let me know if I went too extreme on the slippery-ness of slopes! Not sure if I need to tweak the minimum angle some more for non-ice objects. Main game: Made slanted slopes slippery, can’t just walk up mountains anymore. This also makes sloped ice pieces highly effective. Added green highlight for the "last playthrough" panel on scores that beat your best times. Added green highlight to whatever player in multiplayer had the best time for each level. Made it possible to join multiplayer games mid-game… I think? This might still be buggy at times. Only had limited testing. Should mostly work fine though. Level Editor: Fixed crash bug caused by invalid workshop ID when uploading an update for a workshop level.