Add module performance comparison

[2chevskii]

Summary

Add a reproducible comparison of gly with PSFileIcons 0.1.1, GlyphShell 0.1.1, and Terminal-Icons 0.11.0.

The new
pm run bench:comparison harness pins the compared module versions, measures isolated module import and standard-table formatting over the same 3,000 generated file-system objects, and can emit JSON results. The README includes the median snapshot, while the web documentation records ranges, environment, methodology, reproduction steps, and interpretation limits.

The recorded Windows/PowerShell 7.6.3 snapshot shows gly importing faster than GlyphShell and Terminal-Icons but slower than PSFileIcons. Its standard-table path was slower than all three modules in this workload. The documentation explicitly treats these figures as a single-machine snapshot because the modules format different columns and perform different work.

Validation

• Pester tests — all 47 tests passed with
  pm test
• Documentation build, when documentation changed —
  pm run docs:build passed
• Manual verification, when applicable — full pinned comparison completed successfully; Test-ModuleManifest ./src/gly.psd1 and git diff --check passed

Checklist

• The change is focused and does not include unrelated modifications.
• Tests and documentation have been updated where needed.
• I have read and agree to follow the Code of Conduct.