add demo

src/experimental/demo/lsystem3_demo1.scad

@@ -0,0 +1,18 @@
+use <experimental/lsystem3.scad>;
+use <hull_polyline3d.scad>;
+
+axiom = "A";
+rules = [
+    ["A", "B-F+CFC+F-D&F∧D-F+&&CFC+F+B//"],
+    ["B", "A&F∧CFB∧F∧D∧∧-F-D∧|F∧B|FC∧F∧A//"],
+    ["C", "|D∧|F∧B-F+C∧F∧A&&FA&F∧C+F+B∧F∧D//"],
+    ["D", "|CFB-F+B|FA&F∧A&&FB-F+B|FC//"],
+];
+
+for(line = lsystem3(axiom, rules, 3, 90)) {
+    hull_polyline3d(
+        [line[0], line[1]], 
+        thickness = 0.5, 
+        $fn = 4
+    );
+}