Update to latest zig

[Jarred-Sumner]

The version of zig listed in the readme is 3-ish years old

I was curious what the numbers look like now so I updated it

./a.out is the the c implementation compiled with clang hello.c newplus/plus.c --std=c17 -O2 on macOS

❯ hyperfine "./zig_hello/zig_hello 500000000" "./a.out 500000000"
Benchmark #1: ./zig_hello/zig_hello 500000000
  Time (mean ± σ):     446.2 ms ±   6.8 ms    [User: 443.6 ms, System: 0.9 ms]
  Range (min … max):   437.8 ms … 458.9 ms    10 runs

Benchmark #2: ./a.out 500000000
  Time (mean ± σ):     447.5 ms ±   5.5 ms    [User: 445.0 ms, System: 0.8 ms]
  Range (min … max):   440.4 ms … 456.8 ms    10 runs

Summary
  './zig_hello/zig_hello 500000000' ran
    1.00 ± 0.02 times faster than './a.out 500000000'