lsr: ls with io_uring

Lovely, I might try doing this for some other "classic" utility!

A bit off-topic too, but I'm new to Zig and curious. This here: ``` const allocator = sfb.get();

    var cmd: Command = .{ .arena = allocator };

``` means that all allocations need to be written with an allocator in mind? I.e. one has to pick an allocator per each memory allocation? Or is there a default one?

Caveat emptor, I don't write Zig but followed its development closely for awhile. A core design element of zig is that you shouldn't be stuck with one particular memory model. Zig encourages passing an allocator context around, where those allocators conform to a standardized interface. That means you could pass in different allocators with different performance characteristics at runtime.

But yes, there is a default allocator, std.heap.page_allocator