Update Markdown docs for reflex-dev/reflex#6085

[masenf]

No description provided.

[greptile-apps]

Greptile Summary

Updates markdown documentation and codebase to align with changes in reflex-dev/reflex#6085, which modifies the markdown component API. The key changes are:

• Updated component_map key from codeblock to pre for code block rendering across all files
• Changed heading component functions to accept str instead of list[str] parameters, removing array indexing (text[0] → text)
• Added comprehensive documentation for markdown plugins (default plugins, arbitrary remark/rehype plugins, and plugin options with examples)
• Added support for nested markdown with quadruple backticks (````) through new DemoBlockNestedMarkdown classes
• Updated dependency to point to the masenf/markdown-tlc branch containing the upstream changes

Confidence Score: 4/5

• This PR is safe to merge with low risk, though it depends on an unreleased branch
• The changes are well-structured and consistent across the codebase. The API changes (codeblock → pre, list[str] → str) are applied systematically. The new documentation is comprehensive and helpful. Score is 4/5 (not 5/5) because the reflex dependency points to a feature branch (masenf/markdown-tlc) rather than main or a released version, which means this website cannot be deployed to production until that branch is merged and released
• Pay attention to pyproject.toml - the reflex dependency must be updated back to main or a release version before production deployment

Important Files Changed

Filename	Overview
docs/library/typography/markdown.md	Added comprehensive documentation for markdown plugins including default plugins, arbitrary plugins (remark/rehype), plugin options, and examples. Updated code block syntax and component_map examples to use 'pre' instead of 'codeblock'
pcweb/flexdown.py	Added DemoBlockNestedMarkdown classes to handle nested markdown with quadruple backticks, updated component_map to use 'pre' key instead of 'codeblock' for code block rendering
pcweb/templates/docpage/blocks/headings.py	Changed heading function signatures to accept string instead of list[str], updated functions to use text directly instead of text[0]
pyproject.toml	Updated reflex dependency to point to masenf/markdown-tlc branch instead of main

Sequence Diagram

sequenceDiagram
    participant User
    participant MarkdownDocs as docs/library/typography/markdown.md
    participant Flexdown as pcweb/flexdown.py
    participant Headings as pcweb/templates/docpage/blocks/headings.py
    participant ReactMarkdown as react-markdown (upstream)
    
    Note over ReactMarkdown: react-markdown 10.0.0 changes<br/>'codeblock' → 'pre' in component_map
    
    User->>MarkdownDocs: Read markdown documentation
    MarkdownDocs->>MarkdownDocs: Update examples<br/>codeblock → pre<br/>Add plugin documentation
    
    User->>Flexdown: Render markdown content
    Flexdown->>Flexdown: Update component_map<br/>codeblock → pre<br/>Add DemoBlockNestedMarkdown
    Flexdown->>Headings: Call heading functions with text
    Note over Headings: Changed signature<br/>list[str] → str
    Headings->>Headings: Process text directly<br/>(no more text[0])
    Headings-->>Flexdown: Return rx.Component
    Flexdown-->>User: Rendered markdown
    
    Note over MarkdownDocs,ReactMarkdown: All changes ensure compatibility<br/>with react-markdown 10.0.0

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