Added a new validator for checking if string is a palindrome

[mutahir-muhammad]

Checklist

• PR contains only changes related; no stray files, etc.
• README updated (where applicable)
• Tests written (where applicable)
• References provided in PR (where applicable)

[WikiRik]

What would be use cases for this validator?

[mutahir-muhammad]

What would be use cases for this validator?
This validator can be used to detect if user inputs for passwords are palindromes or not as they are easy to guess and do not provide security. Security systems could use this as a password complexity rule. Other than this, it could be used to identify recurring strings in data and applications can use palindrome detection to create puzzles or challenges. It could also be used as creative leisure by taking inputs that are palindromes.

[WikiRik]

Validation for puzzles or challenges is not something I think belongs in this project, just like creative leisure. I also haven't heard about a password complexity rule for palindromes so I would not be in favour of adding this validator.

[pano9000]

same topic here:
#1935
it got closed down finally, because there is no real use case for a Palindrome Validation, IMHO