feat(library): add constructions of categories, some changes in eq, sigma and path

in eq, add theorem for proof irrelevance and congruence for binary functions
in sigma, add some support for triplets
in path, comment out two unneccesary definitions
in category, add Cat, slice, coslice, product and arrow categories, also add fully bundled approach
feat(library/data/int): remove duplicate theorem, fix one sorry
fix(library/algebra/category): help elaborator

TODO: investigate why we need to help the elaborator here
feat(library/algebra/category): add proof-qed's to reduce compilation time