feat(library/hott) add theorem: if f is an equivalence, so is ap f
chore(library/hott) cleaned up the proof a bit
chore(library/hott) fixed the copyright in equiv_precomp.lean
fix(library/hott) rename IsEquiv.ap to IsEquiv.ap_closed to avoid name clashes
fix(library/hott) rename IsEquiv.ap to IsEquiv.ap_closed to avoid name clashes