Add DownloadableSnippet component

[schultek]

Adds a component for downloading a code snippet as a file. This is displayed as a collapsed code block with additional action buttons in the title.

Provides three options:

• Download directly using browser apis
• Copy code to clipboard
• Expand to show full code

---

I also updated the CopyButton to extract its content from the actual code element instead of taking it as an parameter, to avoid duplicating the data in the output html.

[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 significantly enhances the user experience for interacting with code examples on the site by introducing a versatile SnippetDownloadButton component. This component provides users with convenient options to either download a code snippet as a file, copy its content to their clipboard, or view it in a new tab, directly from the documentation. The change involves both new UI components and a refactoring of how code snippets are presented.

Highlights

• New Snippet Download Component: Introduced a SnippetDownloadButton component that allows users to download code snippets, copy them to the clipboard, or open them in a new browser tab.
• Segmented Button UI: A new SegmentedButton widget and corresponding CSS styles were added to provide a cohesive UI for the download options.
• Code Snippet Integration: The existing game-code.md tutorial snippet was refactored into a .dart file and integrated with the new SnippetDownloadButton component, demonstrating its usage.

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[gemini-code-assist]

Code Review

This pull request introduces a new SnippetDownloadButton component, which is a great enhancement for user experience, allowing users to download, copy, or open code snippets in a new tab. The implementation is well-structured, using a server-side component to fetch the snippet and a client-side component for the user interactions. I've identified a potential memory leak in the client-side component and a minor code clarity issue in the server-side component. My detailed feedback and suggestions for improvement are provided in the comments below.

[flutter-website-bot]

Visit the preview URL for this PR (updated for commit 1b1e2ec):

https://flutter-docs-prod--pr12733-feat-download-code-button-id2rvwh2.web.app

[schultek]

@parlough This is now updated to be a collapsed code block instead of just a button.

[parlough]

This is perfect and works well across the browsers I tested. Thanks for making those adjustments @schultek!