Added Longest Palindrome Subsequence code

[AyushYadav29]

Problem: Given a sequence, find the length of the longest palindromic subsequence in it.
As another example, if the given sequence is “BBABCBCAB”, then the output should be 7 as “BABCBAB” is the longest palindromic subseuqnce in it. “BBBBB” and “BBCBB” are also palindromic subsequences of the given sequence, but not the longest ones.

[pedrovgs]

Thanks for your contribution @AyushYadav29 I'm afraid before reviewing the code we need to add this problem to the readme's list, we need to add information about the problem to solve and the complexity order of your solution's implementation. You can find an example here. Additionally, you should check your code checkstyle and add coverage to your solution. Once you've done this, we will review the code. Thank you in advance!