Add collapsible property

[berge472]

Allows user to make some parents non-collapsible

[geekhybrid]

Looks good. @berge472

However, what do you think about piggybacking on the disabled property?

So, a disabled node cannot be expanded or collapsed, nor can it be dragged or dropped upon?

[berge472]

With disabled the items arent able to be checked/selected. I think their are use cases where we would want the ability to select and item that is not collapsible.

[geekhybrid]

That makes sense. Can you look at why the tests are failing ? I can have a look if you don't find the time.

[berge472]

The Node Version for the test container just needed to be updated. Should be good now

[geekhybrid]

Great work @berge472

[geekhybrid]

Let's updated the README and I'll merge this. Thanks

[berge472]

The README has already been updated

[berge472]

Can you update the npm release with this?

[geekhybrid]

Sure, new version will be available in a few hours.

[geekhybrid]

Can you update the npm release with this?

@berge472 Done.