feat: Add opt-in FFM Twemoji syntax

[Fuyeors]

Summary

• Add opt-in twemojiPlugin and twemojiRule exports for FFM inline emoji rendering.
• Add opt-in latexPlugin, latexInlineRule, and latexBlockRule exports for single-dollar inline and double-dollar block formulas.
• Mirror the monorepo LaTeX behavior while keeping formula text escaped in every renderer.
• Render Twemoji and LaTeX consistently in the core HTML, Lit, and Vue renderers.
• Keep both extensions out of createFuyeorMarkdownParser; consumers must explicitly call .use(twemojiPlugin) and/or .use(latexPlugin).

Validation

• pnpm --filter @fuyeor/markdown-parser typecheck
• pnpm --filter @fuyeor/markdown-parser test:unit
• pnpm --filter @fuyeor/markdown-parser test:ffm
• pnpm --filter @fuyeor/markdown-parser build
• Strict standalone typechecks for Lit and Vue renderers
• pnpm --filter @fuyeor/markdown-parser-playground build
• git diff --check

This PR is intentionally based on fix/parser-performance-security so additional commits can continue to be added before the base PR is merged.

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Project	Deployment	Actions	Updated (UTC)
markdown-parser-playground	Error		Aug 19, 2026 1:37am