The name of the first route to show.
By default, this defers to dart:ui.Window.defaultRouteName.
If this string contains any
/ characters, then the string is split on
those characters and substrings from the start of the string up to each
such character are, in turn, used as routes to push.
For example, if the route
/stocks/HOOLI was used as the initialRoute,
then the Navigator would push the following routes on startup:
/stocks/HOOLI. This enables deep linking while allowing the
application to maintain a predictable route history.
If any of the intermediate routes doesn't exist, it'll simply be skipped.
In the example above, if
/stocks doesn't have a corresponding route in
the app, it'll be skipped and only
/stocks/HOOLI will be pushed.
That said, the full route has to map to something in the app in order for
this to work. In our example,
/stocks/HOOLI has to map to a route in the
app. Otherwise, initialRoute will be ignored and defaultRouteName will
be used instead.
final String initialRoute