input: Write a python function to count occurrences of a keyword in a given text.
  assert count_keyword('Every morning I start my day with a cup of coffee.', 'cup') == 1
  assert count_keyword('She sells sea shells by the sea shore.', 'sea') == 2
  assert count_keyword('Python is great and python is fun.', 'python') == 2
  assert count_keyword('The quick brown fox jumps over the lazy dog.', 'dog') == 1
output: def count_keyword(text, keyword):
      return text.lower().split().count(keyword.lower())