docs: add governance section

[Jatinyadav29]

Summary

This pull request adds a "Governance" section to the documentation.
The content is adapted from the [webpack/governance](https://github.com/webpack/governance) repository’s README file and converted into MDX format to align with the webpack.js.org documentation style and structure.

Related Issue

Fixes [#7333](#7333)

Changes Introduced

• Added new file: src/content/contribute/governance.mdx

• Converted markdown to MDX format with frontmatter and internal link structure

• Added YAML frontmatter:

  ---
  title: Webpack Project Governance
  sort: 15
  contributors:
    - Jatinyadav29
  ---

• Ensured compatibility with the docs build and navigation hierarchy

Preview

The new page introduces details about:

• Roles and responsibilities (Contributors, Committers, Reviewers)
• The Technical Steering Committee (TSC)
• The Consensus Seeking Process

It provides transparency into webpack’s governance model, adapted from Node.js and ESLint governance frameworks.

Checklist

• Converted README to MDX format
• Added appropriate frontmatter and metadata
• Verified formatting and link consistency
• Local build runs without errors
• Linked to the correct issue and mentioned it in the PR body

---

💡 Note: Since I’m still new to the webpack documentation setup, I took extra care to follow the contributing and writer’s guide. Please feel free to suggest any improvements or formatting changes.

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