message: smock: fix typo in readme.md
diff: -# @eth-optimisim/smock
  +# @eth-optimism/smock
  `smock` is a utility package that can generate mock Solidity contracts (for testing). `smock` hooks into a `ethereumjs-vm` instance so that mock contract functions can be written entirely in JavaScript. `smock` currently only supports [Hardhat](http://hardhat.org/), but will be extended to support other testing frameworks.
  