Doing Avent of Code again.

Last year, I used a lot of different languages. It was fun, but it was also a bit of a distraction. This year, I've been using Kotlin lately and it seems like a good opportunity to practice my Kotlin, so I may stick with Kotlin all the way through this year ... or I may not, but I'll definitely be emphasizing Kotlin more than any one language took the forefront last year.