feat: Turtle.SierpinskiTriangle() ( Fixes PoshWeb#21 )

Author: James Brundage

Types/Turtle/SierpinskiTriangle.ps1

@@ -0,0 +1,13 @@
+param(
+    [double]$Size = 200,
+    [int]$Order = 2,
+    [double]$Angle = 120
+)        
+$this.L('F-G-G',  [Ordered]@{
+    F = 'F-G+F+G-F'
+    G = 'GG'
+}, $Order, [Ordered]@{
+    '\+'    = { $this.Rotate($Angle) }
+    '-'     = { $this.Rotate($Angle * -1) }
+    '[FG]'  = { $this.Forward($Size) }
+})