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.

packages/contracts-bedrock/contracts/libraries/Types.sol

@@ -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;