Tweaks to the CAPITALLETTERS files for this project.

[samcunliffe]

File	Description
SECURITY.md	Simplified to provide UCL-specific security contact and upstream reporting instructions
README.md	Added ARC team credit, UCL open-source link, and clarified license/logo usage
CONTRIBUTING.md	Updated with UCL-specific links and guidance on contributing locally vs. upstream

[Copilot]

Pull Request Overview

This PR updates documentation files (SECURITY.md, README.md, and CONTRIBUTING.md) to clarify that this is a UCL fork of the upstream GitHub community projects dashboard, with clear guidance on how to report security issues and contribute to the project.

• Rewrites SECURITY.md to distinguish between UCL-specific and upstream security vulnerabilities
• Updates README.md to credit Advanced Research Computing team and clarify licensing information
• Modifies CONTRIBUTING.md to guide contributors on whether to contribute here or upstream

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
SECURITY.md	Simplified to provide UCL-specific security contact and upstream reporting instructions
README.md	Added ARC team credit, UCL open-source link, and clarified license/logo usage
CONTRIBUTING.md	Updated with UCL-specific links and guidance on contributing locally vs. upstream

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[Copilot]

Pull Request Overview

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

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_{Tip: Customize your code reviews with copilot-instructions.md. Create the file or learn how to get started.}