[FEAT] dynamic data structure addition

updated index.js to dynamically add data structures.

Just add a new file to the structures directory and everything will be updated within the module.

There should be some agreed upon file naming system as this could cause some issues with something like reb-black tree and how one would expect to call it.

In it's current form, it capitalizes the first letter of the file name './dataStructures/', unless the letter at [1]  === '-'. (this handles the case for n-tree).