add convext_hull

src/experimental/demo/convex_hull_demo.scad

@@ -0,0 +1,14 @@
+use <experimental/tri_bisectors.scad>;
+use <experimental/convex_hull.scad>;
+use <shape_starburst.scad>;
+
+xs = rands(-20, 20, 150);
+ys = rands(-20, 20, 150);
+points = [for(i = [0:len(xs) - 1]) [xs[i], ys[i]]];
+
+for(p = points) {
+    translate(p)
+        sphere(.5);
+}
+hull_shape = convex_hull(points);
+#hull_polyline2d(concat(hull_shape, [hull_shape[0]]), width = 1);