Refactor cli.New to reduce memory allocation overhead

[FollowTheProcess]

Summary

Tweaks cli.New to reduce the number of memory allocations it does, some low hanging fruit here it seems...

goos: darwin
goarch: amd64
pkg: github.com/FollowTheProcess/cli
cpu: Intel(R) Core(TM) i5-8257U CPU @ 1.40GHz
      │ before.txt  │             after.txt              │
      │   sec/op    │   sec/op     vs base               │
New-8   2.823µ ± 1%   2.600µ ± 1%  -7.90% (p=0.000 n=10)

      │  before.txt  │              after.txt               │
      │     B/op     │     B/op      vs base                │
New-8   2.720Ki ± 0%   2.250Ki ± 0%  -17.27% (p=0.000 n=10)

      │ before.txt │             after.txt              │
      │ allocs/op  │ allocs/op   vs base                │
New-8   38.00 ± 0%   34.00 ± 0%  -10.53% (p=0.000 n=10)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 91.62%. Comparing base (82da24d) to head (fe9a82f).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #113      +/-   ##
==========================================
- Coverage   91.65%   91.62%   -0.04%     
==========================================
  Files           7        7              
  Lines        1306     1301       -5     
==========================================
- Hits         1197     1192       -5     
  Misses         77       77              
  Partials       32       32              

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