Add support for expressive code in snippets

[khalidabuhakmeh]

This update introduces the handling of expressive code metadata for code snippets, enabling enhanced representation and functionality. Changes include parsing, storing, and rendering expressive attributes in snippets and updates to tests and relevant components to validate the new feature. Additionally, a package dependency (Argon) is updated for compatibility.

Only works for comment snippets currently.

See https://expressive-code.com/ for more details. #714

TL;DR:

This...

<!--begin-snippet: CodeKey(title="Program.cs" {1-3})-->
Console.WriteLine("Hello World");
<!--end-snippet-->

Get converted into...

```csharp title="Program.cs" {1-3}
Console.WriteLine("Hello World");
```

[khalidabuhakmeh]

Also addresses issue #537

[khalidabuhakmeh]

@SimonCropp I can make the expressiveCode parameter optional if it reduces the number of changes in the pull request. I leaned away from doing so in case there's a new parameter in the future and it helped locate all the places I needed to update.

[SimonCropp]

can u add some docs

[khalidabuhakmeh]

@SimonCropp I've made the changes you requested. Please re-review and let me know if you'd like any more changes.

I did notice that #716 was a feature to add metadata at the target. That could be a follow up to this PR where I can make it also handle this metadata at write-time.

[khalidabuhakmeh]

Thank you sir. You are a scholar and a gentlemen. 🧐

[SimonCropp]

lol. thanks. i think i still owe you more drinks than the other way around

i will deploy a beta now. have a play, if u r ok with it, i will deploy a stable when u give me the ok

[SimonCropp]

28.0.0-beta.1 deployed. give nuget 10 min to cache it