This adds a "TCA" feature of a (very) basic transaction history and detail.
It demonstrates a purely state driven navigation stack.
Specifically, a `route: Route?` value is tracked in the state.
This value is driven by the selection of a transaction in the list,
setting it to to `.selectedTransaction(transaction)`,
which then pushes the detail view for that `transaction` onto the `NavigationView`.
Popping the detail view sets the property to `nil`.
Take a look at the previews in `TransactionHistoryView` try them "live" as well.
**N.B** The models are _not_ correct in any way, though are meant to be somewhat representative
and give something to display.
Daniel Haight