input: Write a python function to generate a bar chart for given languages and their counts.
  assert generate_bar_chart(['English', 'Chinese', 'Hindi'], [1.25, 1.21, 0.558]) is None
  assert generate_bar_chart(['Spanish', 'Arabic', 'Portuguese'], [0.455, 0.347, 0.336]) is None
  assert generate_bar_chart(['Russian', 'Japanese', 'German', 'French'], [0.310, 0.282, 0.242, 0.220]) is None
output: def generate_bar_chart(languages, counts):
      import matplotlib.pyplot as plt
      
      plt.figure(figsize=(10, 6))
      plt.bar(languages, counts, color='skyblue')
      plt.xlabel('Languages')
      plt.ylabel('Counts in Billions')
      plt.title('Language Speaker Counts')
      plt.show()