Given a sentence containing multiple words, find the frequency of a given word in that sentence.
Construct a method named 'find_frequency' which accepts two arguments 'sentence' and 'word', both of which are String objects.
Example: The method, given 'Ruby is The best language in the World' and 'the', should return 2 (comparison should be case-insensitive).
Hint: You can use the method
Array#count to count the frequency of
any element in the given array. eg:
[9,3,4,9,5].count(9)Will return the value 2