docs: add v9 section for strong-name signing

[Dor-bl]

PR title

docs: — README-only change, no code/behavior change.

Related issue

Closes # n/a

List of changes

• Added a ## v9 section to the README (placed above ## v8, following the existing per-major-version pattern) documenting that Appium.Net is strong-name signed as of 9.0.0, with the public key token, the Selenium 4.44.0 parity note, and links to #1066 and #1118.
• Replaced the shorter strong-naming blurb that already lived under the ## NuGet section with a one-line pointer to the new ## v9 section, so the same notice isn't duplicated in two places.

Types of changes

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change that adds functionality or value)
• Refactoring (non-breaking change that improves code without altering functionality)
• Breaking change (fix or feature that would cause existing functionality not to work as expected)
• New test coverage (non-breaking change that adds tests for existing, previously untested functionality)
• Test fix (non-breaking change that improves test stability or correctness)
• Chore/Maintenance (updates to build scripts, dependencies, or GitHub Actions)

Tests

• No automated tests (explain why below)

How they run: n/a — README-only documentation change.

Documentation

• Have you proposed a file change/PR with Appium to update documentation?
• Not applicable (no user-facing behaviour change, e.g. tests, CI or maintenance only)

Details

This documents the strong-name signing change already merged in #1118, giving it its own versioned section in the README (matching the existing ## v8 / ## v5 sections) instead of only a short note under ## NuGet.

🤖 Generated with Claude Code

https://claude.ai/code/session_01EsGrPF66RFyVRfLLjRXMh7

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[Dor-bl]

Superseded by #260 — recreated from branch docs/readme-v9-strong-naming (same change) instead of claude/tender-feynman-9317dw, and the commit was amended to drop the co-author trailer. Closing this one.

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