docs: demonstrate how to infer a component's props type

[thenbe]

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Before this PR, there was a simple example to type a variable as the props of some known component.

This PR adds a second example: A generic function that accepts some component and infers the type of its props.

Every now and then I need to create something like this and I always need to look at the source code to recall out how to structure the generic arguments. I figured we should just add an example to the docstring so even users who are not familiar with generics can access it using intellisense.

I also cleaned up the original example a bit.

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[dummdidumm]

The example works for me (it's probably not immediately obvious for people how to do this). Can you run pnpm generate:types in packages/svelte to update the final types? Then we're good to merge.

[dummdidumm]

Thank you!