This is a WIP. Actually I have no time to continue working on this project. Please let me know if you want to contribute. :)
Hierarchical Select for Drupal 8 using Select2.
This module is based on shs and hierarchical_select.
The widget for taxonomy term reference works using the deepest selection.
On D8 you can select multiple Vocabularies. Please select only one for the moment :)
Select2 library will be removed from this module. Probably Select2 will be added to D8 core and for the moment I'm using this library here.