Add CodePreview component

[schultek]

Adds a new CodePreview component to replace usages of the code_and_image partial.

Fixes: #12727

• Column layout (default):

- Row layout:

[gemini-code-assist]

Summary of Changes

Hello @schultek, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request introduces a new CodePreview component, designed to provide a more robust and flexible way to present code snippets alongside visual previews within the documentation. By replacing the older code_and_image partial, this change centralizes the logic and styling for such content, improving consistency and maintainability. The new component supports configurable layouts, allowing for both column and row arrangements of code and preview elements, and includes dedicated styling to ensure a polished presentation.

Highlights

• New CodePreview Component: Introduced a new Dart component named CodePreview to display code blocks alongside preview content, offering a more structured and flexible approach.
• Replaced code_and_image Partial: The new CodePreview component directly replaces the older code_and_image partial, centralizing the logic and presentation for such content.
• Flexible Layout Options: The CodePreview component supports configurable layouts, allowing content to be displayed in either a column (default) or a row arrangement, controlled via a direction attribute.
• CSS Refactoring: Corresponding CSS styles were added for the new .code-preview component, including flexbox properties for responsive layouts, while the deprecated .code-and-image styles were removed.
• Content Migration: Several existing markdown documentation files were updated to utilize the new <CodePreview> component, demonstrating its usage and ensuring consistency across the site.

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[gemini-code-assist]

Code Review

This pull request introduces a new CodePreview component to replace the old code_and_image partial, which is a great improvement for consistency and maintainability. The implementation looks solid, and the refactoring across the markdown files is well-executed.

I've found a couple of issues:

• A high-severity bug in the new CodePreview component where a component attribute is being read with the wrong case, which will prevent it from working as expected.
• A medium-severity theming issue where a hardcoded color is used, which will cause problems in dark mode.
• A medium-severity accessibility issue with incorrect alt text for an image in one of the updated markdown files.

After addressing these points, the PR should be in excellent shape.

[flutter-website-bot]

Visit the preview URL for this PR (updated for commit e5d3bf3):

https://flutter-docs-prod--pr12731-feat-code-preview-component-r7393xt0.web.app

[parlough]

I love love it, much better than I imaged.

Thanks for including the row/col support and the previewcolor is a good idea too.