Added to-absolute method to length.

[Dherse]

Adds the .to-absolute(styles) method to length to allow retrieving a length as absolute (without the em part) when in the right context.

This changes fixes packages like tablex (https://github.com/PgBiel/typst-tablex) that use the following code:

#let measure-pt(len, styles) = {
    let measured-pt = measure(box(width: len), styles).width

    if measured-pt > 0pt {
        return measured-pt
    }

    measured-pt = -measure(box(width: -len), styles).width
    return measured-pt
}

[laurmaedje]

I'm okay with adding this, but think we should discuss the name a bit. resolve is quite generic. Maybe we can find a name that describes more concretely what is happening.

[istudyatuni]

measure, but as a method?

[Dherse]

measure, but as a method?

We discussed this on Discord quickly with @laurmaedje and agreed that to-absolute was a better name since resolve is too generic and measure carries a different meaning.

[laurmaedje]

Thanks!