* Add type hints to k_nearest_neighbours.py
* Refactor k_nearest_neighbours.py into class
* Add documentation to k_nearest_neighbours.py
* Use heap-based priority queue for k_nearest_neighbours.py
* Delete knn_sklearn.py
* updating DIRECTORY.md
* Use optional args in k_nearest_neighbours.py for demo purposes
* Fix wrong function arg in k_nearest_neighbours.py
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