✨ Implement PubspecLineMarkerProvider for pubspec.yaml features

[AlexV525]

Resolves #8511

The PR implements a plugin that provides YAML-related features specifically targeting pubspec.yaml. It includes dependency references currently. Future implementation can be based on this provider.

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[helin24]

Thanks for looking into this! I'm realizing that for this size feature, we probably need to discuss more the functionality you're adding here.

As a starting point:

1. Can you clarify what this adds? The ability to click on versions and see the package on pub.dev, and also some line markers?
2. Can you add a video or screenshots showing what this looks like?
3. Can you describe edge cases that could arise (e.g. the private pub server that you mentioned in the issue) and how we should handle those?

[AlexV525]

After a good night's sleep, I've identified more areas for improvement. I'll update them today. :) But I can definitely give some preview:

1. Can you clarify what this adds? The ability to click on versions and see the package on pub.dev, and also some line markers?
2. Can you add a video or screenshots showing what this looks like?

EDIT: LineMarkerProvider is a provider from IntelliJ that provides the ability to add markers to a single line.

At first glance, you can see the Dart icon is now available at the head of packages.

When you click on any of it:

A pop-up menu shows, you can check several packages about the package, including the home page, the version page, and the API documentation page.

For git/path dependencies:

For overrode dependencies, "Original Dependency" section is available:

3. Can you describe edge cases that could arise (e.g. the private pub server that you mentioned in the issue) and how we should handle those?

Regarding the private server, I'm planning to open a separate request to add a per-project setting to configure pub host after we stabilize this feature, and it should have a lower priority. Other cases, like mirror sites, must live on pub.dev since it's the only effective source to our ecosystem.

The edge cases about the version constraints will be tested in the unit tests.

[helin24]

Great, thanks for the info, it helps me understand a lot more. We'll discuss this feature and approach next week; I recommend waiting until then to continue work on it. Hopefully we can give you clear guidance after convening!