feat(09): add more examples and exercises
feat(09): add more examples and exercises

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