Feature/GitHub file card

[arkdong]

Type of change

• Bug fix (a non-breaking change that fixes an issue)
• New feature (a non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Other (please describe):

Checklist

• I have read the CONTRIBUTING document.
• I have checked to ensure that this Pull Request is not for personal changes.
• I have performed a self-review of my own code.
• My changes generate no new warnings.

Related Issue

Changes

• Added a new ::githubfile directive component in src/plugins/rehype-component-github-file-
  card.mjs that renders a GitHub-style file card and fetches avatar, file size, and last
  modified info from the GitHub API on load.
• Registered the directive in astro.config.mjs so the markdown syntax works site‑wide.
• Extended styles in src/styles/markdown-extend.styl to support the file card infobar (file
  type, size, updated) and its icons.
• Documented usage and parameters with examples in src/content/posts/markdown-extended.md.

How To Test

Screenshots (if applicable)

Additional Notes

[vercel]

@arkdong is attempting to deploy a commit to the zephyirdgmailcom's projects Team on Vercel.

A member of the Team first needs to authorize it.