Proton Support Patch

This patch is intended to allow Duck Game to run flawlessly through Proton on Linux (this hopefully includes the Steam Deck, I haven't got one to test with yet) with mods and all, and without requiring the '-linux' command line option. Something seems to have broken Proton 6 and below as mods are now unable to load textures properly in those versions and there's unfortunately nothing I can do about it on my end. So if you want to play with mods it seems that you need to upgrade to Proton 7 or higher. Please let me know if you're still having any issues running through Proton, and please include your Linux distro, Proton version and crash log if you've got one!

-Updated Steam SDK version
-Fixed issues with toggling fullscreen in Linux (Proton)
-Added onscreen keyboard support when playing in big picture mode
-Duck Game will now automatically detect if it is being run through Proton, the '-linux' command line is no longer necessary. It can still be used incase automatic detection fails, and the '-nolinux' command line option has been added just incase the auto detect returns a false positive in some situations.
-Usability menu now works through Proton
-Fixed a number of issues with Mod types loading incorrectly through Proton (Dord's Weapons and any other assembly with weird characters in it's name such as ' will benefit from this)
-Fixed some rendering issues on Proton