doc: sample: switch to kebab-case

doc/sample/Vehicle.im

@@ -3,8 +3,8 @@ package net.doorstuck.vehicles
 protocol Vehicle
     - startup
     - shutdown
-    - nrWheels
-    - nrDoors
+    - nr-wheels
+    - nr-doors
     - turn(direction:dir)
     - accelerate(direction:dir)
     - velocity
@@ -12,33 +12,33 @@ end
 
 class Car <Vehicle>
     - startup
-        self.engineRunning = true
+        self.engine-running = true
     end
 
     - shutdown
-        self.engineRunning = false
+        self.engine-running = false
     end
 
-    - nrWheels
+    - nr-wheels
         ^4
     end
 
-    - nrDoors
+    - nr-doors
         ^4
     end
 
     - turn(direction:dir)
-        self.currentDirection = dir
+        self.current-direction = dir
     end
 
     - accelerate(direction:dir)
         match dir
-            #forward => self.currentVelocity += 1,
-            #backward => self.currentVelocity -= 1,
+            $forward => self.current-velocity += 1,
+            $backward => self.current-velocity -= 1,
         end
     end
 
-    - velicity
-        ^self.currentVelocity
+    - velocity
+        ^self.current-velocity
     end
 end