Project Euler 70 Solution (#3041)

* Add solution for Project Euler 70, Fixes: #2695

* Remove parameter from solution()

* Add tests for all functions, add fstring and positional arg for solution()

* Rename directory to 070

* Move up explanation to module code block

* Move solution() below helper functions, rename variables

* Remove whitespace from defining min_numerator

* Add whitespace

* Improve type hints with typing.List

Co-authored-by: Dhruv Manilawala <dhruvmanila@gmail.com>