Use <vaadin-grid-tree-toggle> in the cell content
to make a tree UI inside a grid. You need to update the expanded,
level, and leaf properties in your renderer.
NOTE: You must explicitly import vaadin-grid-tree-toggle in order to use it.
Use <vaadin-grid-tree-toggle> in the column body
template to make a tree UI inside a grid. Make sure you have bindings
for the expanded, level, and leaf
properties.