Reduce number of days to 12

[nicolandu]

From 2025 onward, there are only 12 challenges, with day 12 having only one challenge to solve, yet the framework is still set up for 25 challenges. Would it be possible to fix this for next year?

[nicolandu]

It seems #82 is tackling the first issue, but the second one requires keeping a blank part 2 solution.

[fspoettel]

Hi @nicolandu, yes this will be fixed for next year.