feat: add support for remark plugins

[LouisDvr]

📝 Description

This PR adds support for remark plugins to allow users take advantage of the remark ecosystem and extend the lib's behavior (when using plugins that add new nodes, users will have to inject the needed renderers using the customRenderers prop). It finishes the work started in PR #58 by szymonograbek. It also adds a section in the README file to explain how to use plugins with the lib.

📌 Related Issue (Optional)

Link: #43

📷 Screenshots (Optional)

Example using the remark-cjk-friendly plugin.

Before	After

📄 Test Markdown File (Optional)

File 05_cjk_plugin_example.md included in the PR

✅ Checklist

• My PR title follows the Conventional Commit format (e.g. feat:, fix:, chore:)
• This PR addresses the related issue (if applicable)
• I have attached a sample Markdown file (.md) used for testing
• I have attached at least one screenshot of the rendered output (light and/or dark mode preferred)
• I have run pnpm run lint:fix to fix formatting and lint errors
• I have tested the changes in the example app (pnpm i && cd example && pnpm i && pnpm run ios)

[Copilot]

Pull request overview

Adds first-class support for passing Remark plugins into the library’s markdown processing pipeline, enabling consumers to extend parsing/transform behavior via the broader Remark ecosystem.

Changes:

• Introduces a new remarkPlugins prop on Markdown and wires it into the Unified processor.
• Updates the example app and dependencies to demonstrate remark-cjk-friendly.
• Documents plugin usage in the README and adds a sample markdown file for the CJK plugin.

Reviewed changes

Copilot reviewed 5 out of 6 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
src/markdown.tsx	Adds remarkPlugins prop and runs the unified processor with configured remark plugins.
README.md	Documents how to inject remark plugins and updates formatting/examples.
example/App.tsx	Demonstrates remark plugin usage and adds a new sample entry in the loader UI.
example/package.json	Adds remark-cjk-friendly dependency for the example app.
example/pnpm-lock.yaml	Lockfile updates for the example dependency changes.
markdown/05_cjk_plugin_example.md	Adds a markdown sample demonstrating the CJK emphasis behavior fix.

Files not reviewed (1)

• example/pnpm-lock.yaml: Language not supported

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