docs: Add more NatSpec comments

src/DestinationPortal.sol

@@ -6,13 +6,23 @@ import { Ownable } from "@openzeppelin/contracts/access/Ownable.sol";
 
 import { IDestinationPortal } from "./interfaces/IDestinationPortal.sol";
 
+/// @title DestinationPortal.
+/// @author mgnfy-view.
+/// @notice This contract will be deployed on destination chains, and hooked up
+/// with the source portal. This allows seamless, native bridging of the stablecoin
+/// accross multiple evm-compatible networks supported by LayerZero.
 contract DestinationPortal is OFT, IDestinationPortal {
     uint8 private constant DECIMALS = 6;
 
+    /// @notice Sets the ERC20 metadata, layer zero endpoint, and owner contract.
+    /// @param _lzEndpoint The layer zero endpoint address that enables cross-chain OApp communications.
+    /// @param _owner The owner address.
     constructor(address _lzEndpoint, address _owner) OFT("Portal", "PORTAL", _lzEndpoint, _owner) Ownable(_owner) {
         if (_lzEndpoint == address(0) || _owner == address(0)) revert DestinationPortal__AddressZero();
     }
 
+    /// @notice Gets the ERC20's decimals (6).
+    /// @return The token decimals.
     function decimals() public pure override returns (uint8) {
         return DECIMALS;
     }

src/GlobalOwnable.sol

@@ -3,6 +3,12 @@ pragma solidity 0.8.24;
 
 import { Ownable, Ownable2Step } from "@openzeppelin/contracts/access/Ownable2Step.sol";
 
+/// @title GlobalOwnable.
+/// @author mgnfy-view.
+/// @notice This contract owns the `AssetRegistry`, `PythOracle`, and `SourcePortal`
+/// contracts.
 contract GlobalOwnable is Ownable2Step {
+    /// @notice Sets the initial global owner.
+    /// @param _owner The initial global owner address.
     constructor(address _owner) Ownable(_owner) { }
 }