Infer more precise types for `bind:selected` and `let:option`

[janosh]

Figure out if generics (or anything) can be used to infer the type of bind:selected and let:option in slot components correctly from type of options prop. See sveltejs/language-tools#442 (comment) for related question.

[janosh]

Goal is to fix type errors like this:

[Michael-Reich]

Yes, this would help a lot!

[joelmukuthu]

@janosh I'm up for helping with this, just checking to see if perhaps you're already working on it. Let me know if you'd like a PR for this :)

[janosh]

@joelmukuthu Yes, a PR that fixes this would be amazing. 👍

I have no working branch for this yet so feel free to start fresh from main.