TreeView (#725)

* feat(tree-view): add TreeView

* fix(tree-view): select initial active node, correct typedefs

* docs(tree-view): update examples

* chore(tree-view): add test for types

* docs(tree-view): rename example

* docs(tree-view): improve docs

* docs(tree-view): refine examples

* docs: fix invalid syntax

* chore: rebuild component index/api

* docs(layout): increase height of sidenav menu [ci skip]

src/TreeView/index.js

@@ -0,0 +1 @@
+export { default as TreeView } from "./TreeView.svelte";