feat(12): add link to quot implies funext construction
feat(12): add link to quot implies funext construction

fpvandoorn/tutorial,soonhokong/lean-tutorial,cjmazey/fork_leanprover_tutorial,cjmazey/fork_leanprover_tutorial,leanprover/tutorial,fpvandoorn/tutorial,Hodapp87/cs6460_project,avigad/tutorial,cjmazey/fork_leanprover_tutorial,soonhokong/lean-tutorial,Hodapp87/cs6460_project,soonhokong/lean-tutorial,avigad/tutorial,fpvandoorn/tutorial,leanprover/tutorial,Hodapp87/cs6460_project,avigad/tutorial,leanprover/tutorial