docs(readme): bump action version to v5

[adriencaccia]

CodSpeedHQ/action v5.0.0 is out, so the README workflow example now points at it.

Refs COD-3244 (kept open, it tracks the runner release itself)

[greptile-apps]

Greptile Summary

Updates the README’s GitHub Actions workflow example to use CodSpeedHQ/action@v5.

• Replaces the previous @v4 action reference without changing the documented workflow inputs or behavior.

Confidence Score: 5/5

The documentation-only version update appears safe to merge.

The PR changes only the action version shown in the README workflow example, and no blocking or independently actionable issue is established.

Important Files Changed

Filename	Overview
README.md	Updates the documented CodSpeed action major version from v4 to v5; no concrete compatibility issue is established.

_{Reviews (1): Last reviewed commit: "docs(readme): bump action version to v5" | Re-trigger Greptile}

[codspeed-hq]

Performance comparison unavailable

The base and head of this comparison were measured with different runner settings, so their benchmark values are not directly comparable.

What changed between base and head:

• CodSpeed runner v5.0.0 changed how benchmarks are measured (base 4.18.3 → head 5.0.0). View release notes
• Cycle estimation (off → on) changes how benchmark performance is calculated. Learn more about cycle estimation
• Allocator-time exclusion (off → on) removes allocator time from the measurement, which shifts benchmark values. Learn more about allocator-time exclusion
• CodSpeed runner v5.0.0 changed how benchmarks are measured (base 4.18.1 → head 5.0.0). View release notes

Re-run the base with the same settings to get a valid performance comparison.

---

_{Comparing cod-3244-bump-action-v5 (64cbb82) with master (65832cc)}