Export a TypeScript type for 'vaadin-router-location-changed' event

[Haprog]

Currently there is no TS type for the event vaadin-router-location-changed.

Router package should export a type like:

type RouterLocationChangedEvent = CustomEvent<{
  router: Router;
  location: RouterLocation;
}>;

so that it's easy to use the event in TS without having to cast the detail object.