HACKTOBERFEST - Added solution to Euler 64. (#3706)

* Added solution to Euler 64.

Added Python solution to Project Euler Problem 64.
Added a folder problem_064.
Added __init__.py file.
Added sol1.py file.

* Update sol1.py

Made formatting changes as mentioned by pre-commit

* Update sol1.py

Minor changes to variable naming and function calling as mentioned by @ruppysuppy

* Update sol1.py

Changes to function call as mentioned by @cclauss