make calculated intersect numbers available

[sorelfitzgibbon]

It would be great if the calculated numbers for each intersection could be made available in the resulting object.

[dan-knight]

This is very similar to a feature I was discussing with @pboutros and @whelena for CEV. I think this can be achieved in the same way for both packages.

One more nuanced approach might be to extend the resulting S3 object to include another field which stores the calculated data. This will allow it to be treated like a grob when plotting, but also to retain its own calculated data.

Otherwise, they can be simply exported to tsv form (or similar) as a side effect within the function.