Add IResourceWithServiceDiscovery to BunAppResource and VS Code extension recommendations

[Copilot]

Closes #693

Adds IResourceWithServiceDiscovery to BunAppResource for consistency with other runtime resources (DenoAppResource, RustAppExecutableResource, GolangAppExecutableResource, JavaAppExecutableResource) and adds VS Code extension recommendations for the official Bun extension.

Changes

• BunAppResource now implements IResourceWithServiceDiscovery
• Added .vscode/extensions.json to example Bun app recommending oven.bun-vscode
• Added test verifying IResourceWithServiceDiscovery implementation

PR Checklist

• Created a feature/dev branch in your fork (vs. submitting directly from a commit on main)
• Based off latest main branch of toolkit
• PR doesn't include merge commits (always rebase on top of our main, if needed)
• New integration
  • Docs are written
  • Added description of major feature to project description for NuGet package (4000 total character limit, so don't push entire description over that)
• Tests for the changes have been added (for bug fixes / features) (if applicable)
• Contains NO breaking changes
• Every new API (including internal ones) has full XML docs
• Code follows all style conventions

Other information

This aligns Bun with the pattern established by Deno's example which includes .vscode/extensions.json recommending denoland.vscode-deno.

Original prompt

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This section details on the original issue you should resolve

<issue_title>CommunityToolkit.Aspire.Hosting.Bun - using https://marketplace.visualstudio.com/items?itemName=oven.bun-vscode</issue_title>
<issue_description></issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes [CommunityToolkit.Aspire.Hosting.Bun](https://github.com/CommunityToolkit/Aspire/tree/main/src/CommunityToolkit.Aspire.Hosting.Bun) - using https://marketplace.visualstudio.com/items?itemName=oven.bun-vscode #1032

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