Add Chromatic overview documentation

[dev-docs-github-app-dev]

This PR adds a new Chromatic overview documentation page to the project.

The new docusaurus/docs/chromatic/overview.md file provides an introduction to Chromatic, covering the following key areas:

• What is Chromatic?
• Key features of Chromatic, including visual testing, UI review, Storybook integration, and CI/CD integration
• Steps to get started using Chromatic with your project

This overview will help onboard new users to Chromatic and provide a high-level understanding of the platform's capabilities and how it can be integrated into the development workflow. The documentation is intended to complement the existing Chromatic setup and usage guides.

[dev-docs-github-app-dev]

This pull request was created by AI Agent. Please review the changes and provide feedback. Context used:

{
  "docsToCreate": [
    {
      "filePath": "docusaurus/docs/chromatic/overview.md",
      "branch": "main"
    }
  ],
  "docsToUpdate": [],
  "relevantCodeFiles": [],
  "relevantCodeRepo": "team-dev-docs/chromatic-docs",
  "relevantDocsFiles": [
    {
      "filePath": "README.md",
      "branch": "main"
    }
  ]
}