Boolean operations for iron-shapes

This project implements boolean operations on polygons.

The code has been initially forked from https://github.com/21re/rust-geo-booleanop.

Large parts have been rewritten to fit better the needs of electronic design automation tools. This includes for instance support for integer coordinates. Also future work will include finding interactions and overlaps between polygons. This can be used for electrical connectivity checks and netlist extraction from chip layouts.