Ability to load nested items with fetch request

[lubomirblazekcz]

Eg. like here - https://mbraak.github.io/jqTree/examples/05_load_on_demand/

Maybe this could be done custom toggle and with events and methods for now. But native functionality would be still great :)

#2 - I saw in here your current situation with the lib, wish you best of luck with things! Just want to let you know that this is really the best es6 vanillajs nestable lib currently, so if you plan to continue development in the future it would be awesome! Take your time though :)

[Mobius1]

I plan to return to development in the next week or so 👍