Support Some Expressive Code Features

[khalidabuhakmeh]

Expressive code features allow developers to add more metadata to a code block to illustrate the intent of the code block better. For example, you can highlight several lines, highlight symbols via regular expressions, mark text as inserted or deleted, and even perform a diff.

Describe the solution

Allow developers to add additional metadata next to the snippet name that will get added to the code block at render time.

// begin-snippet: App:HelloWorld
// Program.cs
Console.WriteLine("Hello, Again!");
Console.WriteLine("Hello, Again!");
Console.WriteLine("Hello, Again!");
// end-snippet

would become in your C# code

// begin-snippet: App:HelloWorld | {2-2} "Hello" title="Hello 3x"
// Program.cs
Console.WriteLine("Hello, Again!");
Console.WriteLine("Hello, Again!");
Console.WriteLine("Hello, Again!");
// end-snippet

And in markdown would become

<!-- snippet: App:HelloWorld -->
<a id='snippet-App:HelloWorld'></a>
```cs {2-2} "Hello" title="Hello 3x"
// Program.cs
Console.WriteLine("Hello, Again!");
Console.WriteLine("Hello, Again!");
Console.WriteLine("Hello, Again!");
```
<sup><a href='#snippet-App:HelloWorld' title='Start of snippet'>anchor</a></sup>
<!-- endSnippet -->

The resulting output might look something like

Additional context

See Expressive Code at this link. https://starlight.astro.build/guides/authoring-content/#expressive-code-features and here https://github.com/expressive-code/expressive-code/tree/main/packages/astro-expressive-code