message: maint(ctb): add comment to structs in Types
  Adds new custom natspec to structs in the Types file. Undocumented
  fields have created confusion in the past.
diff: @@ -10,6 +10,10 @@ library Types {
  * @notice OutputProposal represents a commitment to the L2 state. The timestamp is the L1
  * timestamp that the output root is posted. This timestamp is used to verify that the
  * finalization period has passed since the output root was submitted.
  + *
  + * @custom:field outputRoot Hash of the L2 output.
  + * @custom:field timestamp Timestamp of the L1 block that the output root was submitted in.
  + * @custom:field l2BlockNumber L2 block number that the output corresponds to.
  */
  struct OutputProposal {
  bytes32 outputRoot;
  @@ -20,6 +24,11 @@ library Types {
  /**
  * @notice Struct representing the elements that are hashed together to generate an output root
  * which itself represents a snapshot of the L2 state.
  + *
  + * @custom:field version Version of the output root.
  + * @custom:field stateRoot Root of the state trie at the block of this output.
  + * @custom:field messagePasserStorageRoot Root of the message passer storage trie.
  + * @custom:field latestBlockhash Hash of the block this output was generated from.
  */
  struct OutputRootProof {
  bytes32 version;
  @@ -31,6 +40,16 @@ library Types {
  /**
  * @notice Struct representing a deposit transaction (L1 => L2 transaction) created by an end
  * user (as opposed to a system deposit transaction generated by the system).
  + *
  + * @custom:field from Address of the sender of the transaction.
  + * @custom:field to Address of the recipient of the transaction.
  + * @custom:field isCreation True if the transaction is a contract creation.
  + * @custom:field value Value to send to the recipient.
  + * @custom:field mint Amount of ETH to mint.
  + * @custom:field gasLimit Gas limit of the transaction.
  + * @custom:field data Data of the transaction.
  + * @custom:field l1BlockHash Hash of the block the transaction was submitted in.
  + * @custom:field logIndex Index of the log in the block the transaction was submitted in.
  */
  struct UserDepositTransaction {
  address from;
  @@ -46,6 +65,13 @@ library Types {
  /**
  * @notice Struct representing a withdrawal transaction.
  + *
  + * @custom:field nonce Nonce of the withdrawal transaction
  + * @custom:field sender Address of the sender of the transaction.
  + * @custom:field target Address of the recipient of the transaction.
  + * @custom:field value Value to send to the recipient.
  + * @custom:field gasLimit Gas limit of the transaction.
  + * @custom:field data Data of the transaction.
  */
  struct WithdrawalTransaction {
  uint256 nonce;
  