refactor: change Route type from ArrayList<> to List<>

the reasoning is (a) that this leaks the implementation detail into the
public API and (2) the the call site usage, e.g.
```
dispatch(SetRouteAction(arrayListOf("route-a", "route-b")
// vs.
dispatch(SetRouteAction(listOf("route-a", "route-b")
```

This does not break API contract, all code using the current version of
ReKotlin-router still compiles fine, because every instance of
`ArrayList` is also a `List`.

Author: Nemo Oudeis

rekotlin-router/src/main/java/org/rekotlinrouter/Routable.kt

@@ -3,7 +3,7 @@ package org.rekotlinrouter
 typealias RoutingCompletionHandler = () -> Unit
 
 typealias RouteElementIdentifier = String
-typealias Route = ArrayList<RouteElementIdentifier>
+typealias Route = List<RouteElementIdentifier>
 
 
 interface Routable {