Add curated topic: runtime-node

[Amnoor]

Please confirm this pull request meets the following requirements:

• I followed the contributing guidelines: https://github.com/github/explore/blob/main/CONTRIBUTING.md.
• This change is not self-promotion.

Which change are you proposing?

• Curating a new topic or collection

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Curating a new topic or collection

• I've formatted my changes as a new folder directory, named for the topic or collection as it appears in the URL on GitHub (e.g. https://github.com/topics/runtime-node)
• My folder contains a runtime-node.png image and index.md
• All required fields in my index.md conform to the Style Guide and API docs: https://github.com/github/explore/tree/main/docs

Why this topic should be curated:
Runtime Node represents a security-first approach to containerization. It is a production-grade, distroless Node.js runtime environment built entirely FROM scratch.

By eliminating the operating system layer, shells, and package managers, it provides a zero-vulnerability base image with a minimal ~45MB footprint. Curating this topic allows the GitHub community to more easily discover hardened, minimalist alternatives for deploying Node.js applications in high-security environments.

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Please note: we will close your PR without comment if you do not check the boxes above and provide ALL requested information.

[Amnoor]

The content validation (test (topics)) is now passing (Green ✅). I have updated the index.md to strictly follow the Style Guide, including fixing the 'open source' hyphenation and adding the logo key.

The Lint job failure appears to be a persistent git checkout error (exit code 1) related to the CI environment for forks. This PR is ready for a manual review or a maintainer-triggered re-run when possible.