feat(robot): add turnBack method

libs/robot.lua

@@ -200,6 +200,16 @@ api.create = function(state, givenConfig)
     return ok, err
   end
 
+  robot.turnBack = function()
+    local ok, errorMessage = robot.turnLeft()
+
+    if not ok then
+      error('turnBack: cannot turn left because ' .. tostring(errorMessage))
+    end
+
+    return robot.turnLeft()
+  end
+
   robot.getState = function()
     return state
   end