🎉 add Solidity verifier subchapter (starknet-edu#235)

* Initializing the solidity verifier sub chapter

* adding foundational topics to boost knowledge

* adding verifiers and sequencers explanations

* adding provers and STARK explanations

* adding SHARP explanations

* adding solidity verifiers intro

* adding prehistoric verifier

* adding solidity verifier contracts

* adding verifiers etherscan addresses as links