Provide utils if don't use EmberRouter

[snewcomer]

After the major upgrade, ember-router-scroll now by default extends EmberRouter. If this doesn't work for some apps that need to extend something other than EmberRouter, we can provide util functions to be called in the constructor to setup the listeners.

I'm unsure who this might apply to so filing an issue for now.

Ref #234

[simonihmig]

I'm unsure who this might apply to so filing an issue for now.

I just came across an IMHO very important use case for having a different solution other than extending from EmberRouter, as @embroider/router also requires this. Having said that, it seems that #255 will achieve the same, without having to expose utils...

[rahulk94]

Seems like we can close this issue now that version 4 is out which extends the router service instead of using a custom router class?