adding turtle examples (#598)

docs/examples.md

@@ -68,6 +68,27 @@ Here are some fun programs for your @boardname@!
 }]
 ```
 
+## Turtle graphics
+
+```codecard
+[{
+  "name": "Turtle Square",
+  "description": "move in a square",
+  "url":"/examples/turtle-square",
+  "cardType": "example"
+}, {
+  "name": "Turtle Spiral",
+  "description": "move in a spiral",
+  "url":"/examples/turtle-spiral",
+  "cardType": "example"  
+}, {
+  "name": "Turtle Scanner",
+  "description": "scans the screen down",
+  "url":"/examples/turtle-scanner",
+  "cardType": "example"  
+}]
+```
+
 ## Actuators
 
 ```codecard

docs/examples/turtle-scanner.md

@@ -0,0 +1,23 @@
+# Turtle Scanner
+
+The turtle keeps on the scanning the screen.
+
+```blocks
+turtle.setPosition(0, 0)
+turtle.turnRight()
+turtle.setSpeed(20)
+basic.forever(() => {
+    turtle.forward(4)
+    turtle.turnRight()
+    turtle.forward(1)
+    turtle.turnRight()
+    turtle.forward(4)
+    turtle.turnLeft()
+    turtle.forward(1)
+    turtle.turnLeft()
+})
+```
+
+```package
+microturtle=github:Microsoft/pxt-microturtle#master
+```

docs/examples/turtle-spiral.md

@@ -0,0 +1,23 @@
+# Turtle Spiral
+
+The turtle goes to the center back and forth.
+
+```blocks
+let index = 0
+turtle.setPosition(0, 0)
+turtle.turnRight()
+basic.forever(() => {
+    for (let index = 0; index <= 4; index++) {
+        turtle.forward(4 - index)
+        turtle.turnRight()
+    }
+    for (let index = 0; index <= 4; index++) {
+        turtle.turnLeft()
+        turtle.back(index)
+    }
+})
+```
+
+```package
+microturtle=github:Microsoft/pxt-microturtle#master
+```

docs/examples/turtle-square.md

@@ -0,0 +1,17 @@
+# Turtle Square
+
+A turtle program that runs in a square.
+
+```blocks
+turtle.setPosition(0, 0)
+turtle.turnRight()
+turtle.setSpeed(29)
+basic.forever(() => {
+    turtle.forward(4)
+    turtle.turnRight()
+})
+```
+
+```package
+microturtle=github:Microsoft/pxt-microturtle#master
+```