Feature Request: add type hint to the selectors properties

[dohooo]

Hi, Thanks for this amazing library.

Can we add type hint to the selectors properties? Just like

const xxx = style({
    selectors: {
        // Each property gets a type hint
        "&":{
            ":nth-child(2n)":{
                ...
            }
        }
    }
})

or

const xxx = style({
    selectors: {
       // Each property gets a type hint
       [`${parent}`]:{
            ":hover":{
                "&":{
                    ":nth-child(2n)":{
                        ...
                    }
                }
            },
            ":focus":{
                "&":{
                    ":nth-child(1n)":{
                        ...
                    }
                }
            },
        }
    }
})

output:
${parent}:hover &:nth-child(2n)
${parent}:focus &:nth-child(1n)

At the moment this is just a preliminary idea and it looks like there will be some holes. But I think we can rely on typescript Template String types to make vanill-extra more type-safe. I think it will enhance a lot of the development experience. I could submit a PR.