Add steam processes to the critical process list.

With only 7 mods enabled mostly targeting explorer, I noticed steam overlay launches in its own blank window when its supposed to be part of the game window, no overlay features work, and steamwebhelper will eventually crash.

Steam is so widely used I think its a reasonable argument to blacklist it, since the program wont be moved to a whitelist by default mechanism.

steam.exe and steamwebhelper.exe.