Be aware that the last sub-list may be smaller than n-items long.
For example chunk 3 [1..10] => [[1,2,3], [4,5,6], [7,8,9], [10]]
mergeBy: (a -> comparable) -> List a -> List a -> List a
Merge two lists. The first argument is a function which returns
the unique ID of each element. Where an element appears more than
once, the last won wins.
Split a list into chunks of length n.
Be aware that the last sub-list may be smaller than n-items long.
For example
chunk 3 [1..10] => [[1,2,3], [4,5,6], [7,8,9], [10]]