[Feature Request] Adding a chamfer option to magnet cutout

[sethkaz]

First of all, thank you for doing the work on this plugin! It's been such a major help and time-saver for me.

I was wondering if I could request adding a chamfer option for the magnet cutout? I've found that press-fitting the magnets is quite challenging when I don't add the chamfer. However, when I add a slight 0.5mm chamfer, it's rather easy.

I'll try to take a crack at doing this myself and putting together a PR for you to review, but you might get to it first.