add TreeSort-Algorithm

[sw-rubix]

https://en.wikipedia.org/wiki/Tree_sort
A tree sort is a sort algorithm that builds a binary search tree from the elements to be sorted, and then traverses the tree (in-order) so that the elements come out in sorted order. Its typical use is sorting elements online: after each insertion, the set of elements seen so far is available in sorted order.
Tree sort can be used as a one-time sort, but it is equivalent to quicksort as both recursively partition the elements based on a pivot, and since quicksort is in-place and has lower overhead, it has few advantages over quicksort. It has better worst case complexity when a self-balancing tree is used, but even more overhead.