Add support for CJK input method editors

[Jenna1337]

I haven't tested it on Linux or Mac, but on Windows using an IME does not produce the desired text. This should be easily fixable with a newer version of SDL, as modern versions actually have proper IME support.

Reference: https://github.com/libsdl-org/SDL/blob/main/src/video/windows/SDL_windowskeyboard.c

[Jenna1337]

Maybe one day Renaud Bédard will upgrade from SDL version FEZ uses. I'm contemplating creating an issue in https://github.com/renaudbedard/fez-1.12-issues to ask him to update from SDL2 to SDL3