Added new algorithm: cracking caesar cipher with the chi-squared test (#1950)

* added decrypt_caesar_with_chi_squared.py and ran all checks

* Updated default parameters

Removed mistake with mutable default arguments

Co-authored-by: Christian Clauss <[email protected]>

* Updated handling for optional arguments

Co-authored-by: Christian Clauss <[email protected]>

* Changed return statement to tuple

Made function return a tuple instead of a list

* Added more doctests

* Fixed spelling mistakes

* black . - reformatted decrypt_caesar_with_chi_squared.py

* Updated if statements to fit the updated code

* Minimized amount of lines in the code.

Co-authored-by: Christian Clauss <[email protected]>