Support syntax to pass multiple multiline code blocks as props (not slots)

[nirtamir2]

Hi
I created a <playgrounds> component in Vue and I render it in the slides.md.
This component requires to accept props code for multi-line code snippets as Array<string>.
I did not find a nice way to render it inside the markdown.

I could render it like:

::playgrounds{:code=`["export default function A(){ \n return <h1>hi</h1> }", "const b = 2", "const c = a + b"]`}
::

Using mdc does not support the MDC YAML format because slidev treats it as a new slide.

I could think of an interface like the slots in a layout:

::code-0::

```tsx
export default function App() {
  return (
    <Canvas>
      <ambientLight />
      <mesh>
        <boxGeometry />
        <meshStandardMaterial />
      </mesh>
    </Canvas>
  )
}
\```

::code-1::

<BrowserWrapper>
  <DemoIframe url="/demo/basic" />
</BrowserWrapper>

---

But I need the props to be as strings instead of slots (because I don't render them directly to the dom), and I need it as an array.
The advantage of this syntax is that it support multi-lines, easy to read and formatted well with tools.

What do you think? I'm open to suggestions, but currently I don't like that I need to render the component prop array in a single and use \n or escaping. A new syntax for it / support syntax to convert named slots syntax in markdwon as regular props would be nice