Devalapurkar & Haine
This is a formalization of results described in #1147, with the two main results being the stable James splitting ΣΩΣX ≃ ΣX ⋁ Σ(X ⋀ ΩΣX) and the Hilton–Milnor splitting Ω(X ⋁ Y) ≃ ΩX × ΩY × ΩΣ(ΩY ⋀ ΩX). ~~It still needs cleaning up and merging with #1151, but most of it is done.~~
I'm putting the HM splitting in the Homotopy folder, but the James splitting in the HITs.James folder, because the latter result is quite related to what's already in there.
Oh wait, should I rebase on #1133?
Another question is, should I add the public imports in Cubical.HITs.James and Cubical.HITs.Susp for the new lemmas?
This should be everything, so it's ready for review.
I went ahead and made some changes, particularly to prefer copatterns over record syntax where it's not too inconvenient and to make some type signatures more explicit. Does everything look OK to you? If so (and CI passes) I will merge.
Yes, this looks great!
Thanks for the contribution (and sorry for the long wait)!