Added a hex-bin.py file in conversion.py (#4433)

* Added a file that converts hexa to binary

* Added file to convert hexadecimal to binary

* Update hex-bin.py

* added type hint in the code

* Added doctest

* Added code to handle exception

* Resolved doctest issue

* Update hex-bin.py

* Modified convert function

* Added WhiteSpace around operators.

* Made more pythonic

* removed whitespace

* Updated doctest command

* Removed whitespace

* imported union

* Replaced flag with is_negative

* updated return type

* removed pip command

* Resolved doctest issue

* Resolved doctest error

* Reformated the code

* Changes function name

* Changed exception handling statements

* Update and rename hex-bin.py to hex_to_bin.py

* Update newton_method.py

* Update matrix_operation.py

* Update can_string_be_rearranged_as_palindrome.py

* Update hex_to_bin.py

Co-authored-by: Christian Clauss <cclauss@me.com>