feat: shiki magic move integration

[antfu]

Here is the example usage:

slidev/demo/starter/slides.md

Lines 180 to 230 in f1d967b

	# Shiki Magic Move
	(this feature is still experimental)
	Powered by [shiki-magic-move](https://shiki-magic-move.netlify.app/), Slidev supports animations across multiple code snippets.
	Add multiple code blocks and wrap them with <code>````md magic-move</code> (four backticks) to enable the magic move. For example:
	````md magic-move
	```ts
	const author = reactive({
	name: 'John Doe',
	books: [
	'Vue 2 - Advanced Guide',
	'Vue 3 - Basic Guide',
	'Vue 4 - The Mystery'
	]
	})
	```
	```ts
	export default {
	data() {
	return {
	author: {
	name: 'John Doe',
	books: [
	'Vue 2 - Advanced Guide',
	'Vue 3 - Basic Guide',
	'Vue 4 - The Mystery'
	]
	}
	}
	}
	}
	```
	```ts
	export default {
	data: () => ({
	author: {
	name: 'John Doe',
	books: [
	'Vue 2 - Advanced Guide',
	'Vue 3 - Basic Guide',
	'Vue 4 - The Mystery'
	]
	}
	})
	}
	```
	````

Screen.Recording.2024-02-26.at.13.33.13.mov

[John98Zakaria]

Please tell me if I could help with that feature, I was working on implementing it myself, but now I don't need to 😅