@ngrx/router-store: StoreRouterConfig should use generics to better support custom serializer

[homj]

Replacing the built in serializer with a custom one results in a type warning, when using a selector in the StoreRouterConfig:

interface MyRouterState extends BaseRouterStoreState {
    customParam: any;
}

class MyRouterStateSerializer extends RouterStateSerializer<MyRouterState> {
    // ...
}

const selectRouter: Selector<any, RouterReducerState<MyRouterState>> = // ...;

// in the Module:
StoreRouterConnectingModule.forRoot({
    stateKey: selectRouter,
    serializer: MyRouterStateSerializer
})

results in the warning:

TS2322:
Type 'MemoizedSelector<object, RouterReducerState<MyRouterState>>' is not assignable to type 'StateKeyOrSelector'.
Type 'MemoizedSelector<object, RouterReducerState<MyRouterState>>' is not assignable to type 'Selector<any, RouterReducerState<SerializedRouterStateSnapshot>>'.
Type 'RouterReducerState<MyRouterState>' is not assignable to type 'RouterReducerState<SerializedRouterStateSnapshot>'.
Types of property 'state' are incompatible.
Type 'MyRouterState' is not assignable to type 'SerializedRouterStateSnapshot'.
Property 'root' is missing in type 'MyRouterState'.

The proposed change would be to use generics on StateKeyOrSelector and StoreRouterConfig:

export declare type StateKeyOrSelector<ROUTER_STATE extends BaseRouterStoreState = SerializedRouterStateSnapshot> = string | Selector<any, RouterReducerState<ROUTER_STATE>>;

export interface StoreRouterConfig<ROUTER_STATE extends BaseRouterStoreState = SerializedRouterStateSnapshot> {
  stateKey?: StateKeyOrSelector<ROUTER_STATE>;
  serializer?: new (...args: any[]) => RouterStateSerializer<ROUTER_STATE>;
  navigationActionTiming?: NavigationActionTiming;
}

Describe any alternatives/workarounds you're currently using

Currently, the only way to prevent this issue is not typing the selector correctly (which is bad imo), or suppressing the warning with @ts-ignore (which is also not great, since it makes me wonder whether the root property of SerializedRouterStateSnapshot is necessary or not)

Other information:

Demo on StackBlitz

If accepted, I would be willing to submit a PR for this feature

[ ] Yes (Assistance is provided if you need help submitting a pull request)
[x] No