Add Markstream streaming Markdown renderer

[Simon-He95]

Description

Adds Markstream as a frontend UI Library for rendering incomplete Markdown in streaming AI-chat responses.

Type of Change

• 📚 Documentation update

Resource Addition/Update

• This PR adds a new resource
• This PR updates an existing resource
• This PR removes an outdated resource

Resource Details (if applicable)

• Title: Markstream
• URL: https://markstream.simonhe.me/
• Category: UI Library
• Description: Open-source streaming Markdown renderer for AI chat interfaces, with incomplete-token handling, Mermaid, KaTeX, syntax highlighting, safe HTML, and SSR across major frontend frameworks.
• Tags: markdown, ai, streaming, vue, react, svelte, angular, ssr

Checklist

• My code follows the project's style guidelines
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have updated the documentation accordingly (if applicable)
• My changes generate no new warnings or errors
• I have added tests that prove my fix is effective or that my feature works (if applicable)
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published

Screenshots (if applicable)

Not applicable — this is a JSON resource-catalog entry.

Related Issues

Closes #

Additional Notes

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