Added IO module documentation link to toplevel README.md
Added IO module documentation link to toplevel README.md

floooh/oryol,floooh/oryol,floooh/oryol,aonorin/oryol,aonorin/oryol,aonorin/oryol,floooh/oryol,floooh/oryol,aonorin/oryol,aonorin/oryol,aonorin/oryol,aonorin/oryol,floooh/oryol