add px_union

src/experimental/px_union.scad

@@ -0,0 +1,8 @@
+use <util/sort.scad>;
+use <util/dedup.scad>;
+
+function px_union(points1, points2) =
+    dedup(
+        sort(concat(points1, points2), by = "vt"), 
+        sorted = true
+    );