Method to complete clustering of Timeline Items

[DavidSpackman]

Same as #3859
I would like to add ability to cluster Timeline items into the current vis.js release.

My current work so far has been to replicate the exports.stack functionality called from Group.prototype._redrawItems and hide the colliding items.
I am then planning to create a new item to represent the clustered items. However I'm not sure if it's possible to create new items from within the "group" content.
I tired to add a new item via timeline.itemsData.add() within Group.prototype._redrawItems however this created an infinite loop due

Any direction on how I can re-add the clustering functionality to the timeline?
(There is a method suggested in #3859, however I need a bit more explanation on how to achieve this)