nestedBranches property
These go always before the routes. These are visualized using a nested Router inside current page.
These don't have to fully overlap the current page.
There are no nested branches when null.
NOTICE: when a node has nested routes, there cannot be the node displayed only by itself. Nested routes need to be displayed, too. Meaning that the URL has to contain one of the nested branches with at least one page in the nested stack. This applies recursively to the nested branch nodes, too.
Implementation
final NestedBranches<T>? nestedBranches;