[TS] Fix missing default Page type export

[Philzen]

As the title says. Fixes the last TypeScript error in packages/router/src/__tests__/pageLoadingContext.test.tsx.

[Philzen]

@Tobbe do you think we could easily introduce a typecheck job (similar to yarn rw tc in RW projects) into the CI and start fixing & including files and folders incrementally?

Not sure if there were any rules of engagement regarding this approach in the past, the downside here is of course slightly increased CI runtime and a slower iteration cycles. But the advantages could be worth it, especially we could never break working and tested types again in new releases – thinking of all the commits that were just rolled back in the Router Set type for example, which would never have been merged in the first place if such a job was in place.

[Philzen]

@Tobbe do you think we could easily introduce a typecheck job (similar to yarn rw tc in RW projects) into the CI and start fixing & including files and folders incrementally?

Ahh it looks like there already exists something like that:

However it apparently does not check the tests folder – which i believe should be included as they are the actual application of the types.