ICustomToken.sol Spec

Minimum expected interface for L1 custom token (see TestCustomTokenL1.sol for an example implementation)

registerTokenOnL2(address l2CustomTokenAddress, uint256 maxSubmissionCost, uint256 maxGas, uint256 gasPriceBid) (external)

Should make an external call to EthERC20Bridge.registerCustomL2Token

transferFrom(address sender, address recipient, uint256 amount) → bool (external)

balanceOf(address account) → uint256 (external)