feat: Change date_range 'holidays' type-annotation to Collection instead of Sequence

[aleewen]

In date_range, the argument holidays takes a Sequence[date] annotation. However, because ordering doesn't matter here, this can be changed to Collection[date]. I suspect that other arguments across the repo may be able to change as well to allow the type-checker to resolve properly.

Thanks!

[MarcoGorelli]

sure sounds good

[aleewen]

Thanks!
Big fan of your Polars plugin tutorial as well.