fix(challenges): add solution, test to project euler problems

This commit achieves the following:
Add solution to problems: 21, 25, 29, 35, 55
Add/modify tests to problems: 5, 12, 14, 25, 55
Update description to problems: 2, 3, 4, 5, 6, 7, 8, 9, 11, 12, 14, 15, 16, 17, 55

fix(challenges): add solution and tests for project euler problem 55

Added solution and tests to evaluate problem 55 of Project Euler challenges.