Support WQXGA(2560x1600) borderless window mode

[박현우]

For 16:10 QHD users, could you add 2560 x 1600 mode here?

For future proofing, maybe adding generic 16:9 & 16:10 mode could help, too.
I just want the game to scale fullscreen. I don't care letterboxing or blurry texture.
High-resolution texture isn't necessary.