feat: vitest added and updated unique classnames logic

[ITZSHOAIB]

Description

Related Issues

• Issue:

Type of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

Checklist:

• I have checked that there isn't already a PR that solves the problem the same way.
• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have included a changeset according to the type of my changes
• I have added tests to cover my changes.
• All new and existing tests passed.

Additional Context or Notes

• Is there anything specific the reviewer should focus on?

[changeset-bot]

🦋 Changeset detected

Latest commit: f88b774

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
rehype-code-group	Patch

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