Add a take/2 task

[gausby]

If we do this workshop again we should consider adding a take/2 task to the assignments.

All groups ended up having two accumulators in their solution, because all the previous assignments up until chunk/2 could be solved using accumulators. Only one group had an alternative solution that used a take/2 helper function.

Learning how to juggle two accumulators are good, but I guess learning how to opt for a helper for some of the heavy lifting is a good lesson too. Just look at this diff: gausby@bd454b9

Question is though; should the take/2 assignment come before the chunk/2 assignment, or should it come earlier as it is rather "easy"¹ to implement? The former would make it obvious that it can help solving chunk, the latter would hide it a bit, letting the student think a bit before reaching for take/2.

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¹ "easy" to implement compared to the other functions