fact: Definition two_sided_disp_cat_weq_disp_cat : twosided_disp_cat C₁ C₂ ≃ disp_cat (category_binproduct C₁ C₂).
imports: UniMath.Foundations.All UniMath.MoreFoundations.All UniMath.CategoryTheory.Core.Categories UniMath.CategoryTheory.DisplayedCats.Core UniMath.CategoryTheory.PrecategoryBinProduct