fix: add style.css for error-handling.mdx

[Rezn1r]

Summary

Information

• This PR fixes an issue.
• This PR adds something new (e.g. new method or parameters).
• This PR is a breaking change (e.g. methods or parameters removed/renamed).
• This PR is not a code change (e.g. documentation, README, typehinting,
  examples, ...).

Checklist

• [x ] I have searched the open pull requests for duplicates.
• If code changes were made then they have been tested.
  • I have updated the documentation to reflect the changes.
• If type: ignore comments were used, a comment is also left explaining why.
• I have updated the changelog to include these changes.

[Copilot]

Pull request overview

This pull request adds a missing CSS import statement for the discord-message-components package in the error-handling.mdx documentation file.

Changes:

• Adds the required style.css import for discord-message-components to ensure proper styling of Discord UI components used in the error handling documentation

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