docs: add hero GIF to README

[mfaferek93]

Pull Request

Summary

just hero gif added to README

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Issue

Link the related issue (required):

• closes N/A

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Type

• Bug fix
• New feature or tests
• Breaking change
• Documentation only

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Testing

How was this tested / how should reviewers verify it?

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Checklist

• Breaking changes are clearly described (and announced in docs / changelog if needed)
• Tests were added or updated if needed
• Docs were updated if behavior or public API changed

[Copilot]

Pull request overview

Adds a centered “hero” animation to the project’s top-level README to improve the landing-page presentation for the ros2_medkit diagnostics gateway.

Changes:

• Insert a centered <img> tag near the top of README.md to display hero-full.gif.