Router: wait for page unmount before changing route and query parameters

[Bleuzen]

Feature request

Is your feature request related to a problem? Please describe.

When using animation libraries to make page transitions, the router doesn't wait for the exit animation to finish before changing the route and query parameters. The creates the problem that the old page during fade-out is re-rendered again with the route and query parameters of the new page it is transitioning to.

Describe the solution you'd like

Do not change route and query parameters before old page is completely unmounted.

Additional context

For an example, see this issue:
illinois/next-page-transitions#23 (comment)