feat(relations_in_lean): improve exposition and more examples
feat(relations_in_lean): improve exposition and more examples

fpvandoorn/logic_and_proof,rlewis1988/logic_and_proof,rlewis1988/logic_and_proof,rlewis1988/logic_and_proof,avigad/logic_and_proof,leanprover/logic_and_proof,fpvandoorn/logic_and_proof,fpvandoorn/logic_and_proof,leanprover/logic_and_proof,avigad/logic_and_proof,avigad/logic_and_proof,leanprover/logic_and_proof