docs: add mini-poml-rs community project

[ultmaster]

Summary

• document the experimental Rust-based POML renderer mini-poml-rs in a new ecosystem section

Testing

• npm run build-webview
• npm run build-cli
• npm run lint
• npm test
• python -m pytest python/tests

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https://chatgpt.com/codex/tasks/task_e_68a2bca1ed30832e890034b24217a708

[Copilot]

Pull Request Overview

This PR documents a community-contributed Rust implementation of the POML renderer by adding a new "Ecosystem & Community Projects" section to the project documentation.

• Adds documentation for mini-poml-rs, an experimental Rust-based POML renderer
• Creates a new ecosystem section to highlight community contributions
• Provides context that this implementation serves environments without JavaScript or Python interpreters

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
docs/index.md	Adds new ecosystem section with mini-poml-rs project reference
README.md	Adds matching ecosystem section for consistency across documentation

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