Assign CODEOWNERS

[gakonst]

The CODEOWNERS.md should be updated to include who owns what.

[smartcontracts]

I'd like to be assigned the following:

l2geth/*
packages/smock/*
packages/core-utils/*
packages/contracts/*
packages/hardhat-ovm/*

I could potentially also take a codeowner role for packages/data-transport-layer/* but happy to pass that off to someone else.

[maurelian]

packages/contracts/*

I'd also like to follow smock and core-utils more closely and hopefully support @smartcontracts with that, so let's add:
packages/smock/*
packages/core-utils/*

[annieke]

packages/batch-submitter/*
also down to be on packages/data-transport-layer/* and packages/core-utils/* if necessary

[tynes]

l2geth/*
ops/* (assuming @gakonst isn't going to maintain long term)
integration-tests/*

[karlfloersch]

batch-submitter for sure
l2geth while we don't have more folks working on it
Can also do ops to support Mark while we don't have more folks working on it

[K-Ho]

Can own packages/core-utils/watcher , message-relayer

[ben-chain]

packages/contracts/*
packages/core-utils/* if that isn't overloaded, I want to follow more but don't have much experience