Day 13 solution

Honestly I think I have an error somewhere in the part 2 logic because my final output characters weren't exactly correct, but they were close enough that my first guess for each letter was right. So I may revisit this to find and fix the logic bug, but apparently it's Close Enough™ to be done for the night.

src/main.cs

@@ -30,7 +30,8 @@ else
         "9" => new Day09(),
         "10" => new Day10(),
         "11" => new Day11(),
-        _ => new Day12(),
+        "12" => new Day12(),
+        _ => new Day13(),
     };
     day.Go();
 }