Advent of Code 2020: Day 2 (Ruby solution)

This time, the tasks are to count valid passwords from a text file. Each line of text contains two numbers, a letter, and a password. Example input: 1-8 n: dpwpmhknmnlglhjtrbpx 11-12 n: frpknnndpntnncnnnnn 4-8 t: tmttdtnttkr 12-18 v: vvvvvvvqvvvvvqvv...