Add instruction on how to build a car

Author: Ambrose Cheung

english/build-a-car/build-a-car.md

@@ -1,5 +1,6 @@
 Make the body. Make the frame. Add some paint.
 Build the interior. Build the chassis.
 Add a motor. Add the wheels.
+Pump the wheels fully. Add interior seats.
 
 [Drive your new car back to the story](../marshmallow.md)