Add supports_alpha()->bool for PixelFormatEnum
Add supports_alpha()->bool for PixelFormatEnum

Cobrand/rust-sdl2,AngryLawyer/rust-sdl2,Rust-SDL2/rust-sdl2,Cobrand/rust-sdl2,Cobrand/rust-sdl2,Rust-SDL2/rust-sdl2,Rust-SDL2/rust-sdl2