std/fmt/index.zig: support printing hex bytes on slices;
std/fmt/index.zig: support printing hex bytes on slices;

zig-lang/zig,raulgrell/zig,raulgrell/zig,zig-lang/zig,raulgrell/zig,zig-lang/zig,raulgrell/zig,andrewrk/zig,raulgrell/zig,andrewrk/zig