Descriptions for turtle examples (#599)

docs/examples/turtle-scanner.md

@@ -1,6 +1,6 @@
 # Turtle Scanner
 
-The turtle keeps on the scanning the screen.
+The turtle scans the display over and over again.
 
 ```blocks
 turtle.setPosition(0, 0)

docs/examples/turtle-spiral.md

@@ -1,6 +1,6 @@
 # Turtle Spiral
 
-The turtle goes to the center back and forth.
+A turtle that spirals into the center of the display and back out again.
 
 ```blocks
 let index = 0

docs/examples/turtle-square.md

@@ -1,6 +1,6 @@
 # Turtle Square
 
-A turtle program that runs in a square.
+A turtle that traces a square pattern.
 
 ```blocks
 turtle.setPosition(0, 0)