Regression tests

[sebastian-goeldi]

Would be nice to have many of the tests also have regression tests like gdsfactory does.

[joamatab]

How about we move that part to kfactory and kfactory can use it too?

it purely depends on klayout

[sebastian-goeldi]

yeah, absolutely. I was just being cheeky when I added help wanted ^^.

I think it would be great if we can add it, but it's not urgent at all