add: unit variable support

[sivertjoe]

context 🐦

I added this to my/the template

let fmt = std::env::var("TASKUNIT").unwrap_or("ms".to_owned());
let (u, elapsed) = match fmt.as_str() {
    "ms" => ("ms", elapsed.as_millis()),
    "ns" => ("ns", elapsed.as_nanos()),
    "us" => ("μs", elapsed.as_micros()),
    "s" => ("s", elapsed.as_secs() as u128),
    _ => panic!("unsupported time format"),
};

So that I can run TASKUNIT=us cargo aoc run and get the microsecond performance, for instance

This code breaks the tally, and , more importantly, run -S 1|2 command, so I had to fix that

Let me know what you think

[seblyng]

Nice🙌