add version notes to README
add version notes to README

Rust-SDL2/rust-sdl2,Rust-SDL2/rust-sdl2,Cobrand/rust-sdl2,vadixidav/rust-sdl2,andelf/rust-sdl2_gfx,Cobrand/rust-sdl2,Rust-SDL2/rust-sdl2,Cobrand/rust-sdl2,AngryLawyer/rust-sdl2