We use a different proof strategy for the naturality than pursued the last week.
We proof the unpointed version of the naturality by generalizing it from loops to paths so that we can apply path induction.
For the pointed version, we do some ugly calculations to cancel noncomputable applications of funext
The construction of the Serre spectral sequence is done up to 11 sorry's, all which are marked with 'TODO FOR SSS'. 8 of them are equivalences related to cohomology (6 of which are corollaries of the other 2), 2 of them are calculations on int, and the last is in the definition of a spectrum map.
Note: the Serre spectral sequence only works for unreduced cohomology, so we need some results for that
For reduced homology we might get a similar result if we replace the sigma in the RHS by a dependent version of the smash product
