Add test to validate contributor listing format and confirm current state

[Copilot]

This PR addresses the contributor listing sorting requirements by analyzing the current state and adding validation.

Analysis Results

After thoroughly examining both README.md and CONTRIBUTING.md, I found that:

• ✅ All contributor listings are already sorted alphabetically by first name
• ✅ No company affiliations exist in emeritus sections that need removal
• ✅ CONTRIBUTING.md contains no contributor listings to sort

The current state of README.md already meets all requirements:

• Maintainers section: Correctly sorted (Alex → Andrzej → Antoine → Bogdan → Dmitrii → Evan → Pablo → Sean → Tyler → Yang)
• Approvers section: Correctly sorted (Christos → Curtis → David → John → Matt → Moritz → Sam → Ziqi)
• Emeritus Maintainers section: Correctly sorted (Daniel → Juraci → Tigran) with no company affiliations
• Emeritus Approvers section: Correctly sorted (Anthony → Bryan → Przemek → Ruslan) with no company affiliations

Changes Made

Since the contributor listings were already properly formatted, I've added a comprehensive Go test (tests/contributor_test.go) to ensure this format is maintained in the future. The test validates:

1. All contributor sections are sorted alphabetically by first name (case-insensitive)
2. Emeritus sections contain no company affiliations
3. Proper handling of special name cases (e.g., "John L. Peterson (Jack)")

The test runs successfully and integrates with the existing test infrastructure.

Fixes #29.

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