fix: fix the discrepancy in password guesses between zxcvbn and zxcvbn4j

[vvatanabe]

Describe the change

Fix the discrepancy in password guesses between zxcvbn and zxcvbn4j.

Describe your solution

• The constant REFERENCE_YEAR was changed to get the current year.
• Fixed the logic of possibleYearSplits in DateMatcher.

Tests

• Add DateGuessTest to ScoringTest.
• Add date pattern to MatchingTest.

Additional context
Issue: #151

[coveralls]

coverage: 92.662% (-0.02%) from 92.68% when pulling 44dda11 on fix-the-discrepancy-in-password-guesses-between-zxcvbn-and-zxcvbn4j into a213a44 on main.