fix and add types in .d.ts file (#77)

* fix and add types in .d.ts file

* Update Dependencies

* Added "depth" as computed property + css var of cursor

* Type tweaks

add crossbrowser no-select

update to 1.8.1

add sourcemap

add isDraggable and isSelectable

Merge branch 'master' of github.com:holiber/sl-vue-tree

improve drop on the bottom of tree

fix select and getNode