input: Write a python function to plot the number of orders per day in a month using matplotlib.
  assert plot_orders([1,2,3,4,5,6,7,8,9,10,11,12], [10, 20, 30, 5, 10, 15, 25, 10, 20, 15, 5, 10])==None
output: def plot_orders(days, orders):
      import matplotlib.pyplot as plt
      
      plt.figure(figsize=(10, 5))
      plt.plot(days, orders, marker='o')
      plt.title('Number of Orders Per Day in a Month')
      plt.xlabel('Day')
      plt.ylabel('Number of Orders')
      plt.grid(True)
      plt.show()