fix: joins, cuts and sketch profiles where outlines touch at a point (#841)

Fixes #588.

crates/kernel/src/lib.rs

@@ -56,6 +56,8 @@ mod numbered;
 mod offset;
 mod ops;
 mod par;
+#[cfg(test)]
+mod pinch_tests;
 mod plane_fit;
 mod polybool;
 mod polyhedron;