Proper typing for $page.data.session?

[AaronFlynn1989]

Describe the problem

I feel like I'm missing something obvious. $session was removed in #5946 and the alternative proposed in #5883 is using layout load functions and retrieving the session info there and then returning it as part of the data; which I am doing, but I'm not sure how I should have proper typing for $page.data.session?! Previously I was declared the type in app.d.ts's App.Session, and then using the typed $session store everywhere, which was very convenient, I don't know how I'm supposed to achieve something similar now?!

Importance

i cannot use svelte without it

[AaronFlynn1989]

Sorry, should've created this issue in the kit repo, my bad.