Allow changing number of threads with env variable

[saulshanabrook]

No description provided.

[saulshanabrook]

@actions-user changelog

[Copilot]

Pull Request Overview

This PR adds support for configuring the number of Rayon threads used by the underlying Rust library through the RAYON_NUM_THREADS environment variable, with a fallback default of 1 thread when the variable is unset or invalid.

• Replaces hardcoded single-thread configuration with environment variable-based thread count
• Adds documentation explaining the new parallelism configuration option
• Updates changelog to reflect the new feature

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
src/lib.rs	Implements environment variable parsing for thread count configuration
docs/reference/usage.md	Documents the new parallelism configuration feature
docs/changelog.md	Records the feature addition in the unreleased section

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[codspeed-hq]

CodSpeed Instrumentation Performance Report

Merging #330 will not alter performance

_{Comparing env (ac272a3) with main (9cc65a9)¹}

Summary

✅ 7 untouched benchmarks

Footnotes

1. No successful run was found on main (ac272a3) during the generation of this report, so 9cc65a9 was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩