Add C4 audit, start to add weth router

pkg/sol/IWETH10.sol

@@ -0,0 +1,15 @@
+// SPDX-Identifier: MIT
+
+pragma solidity 0.8.16;
+
+interface IWETH10 {
+    /// @dev `msg.value` of ETH sent to this contract grants caller account a matching increase in WETH10 token balance.
+    /// Emits {Transfer} event to reflect WETH10 token mint of `msg.value` from `address(0)` to caller account.
+    function deposit() external payable;
+
+    /// @dev Burn `value` WETH10 token from caller account and withdraw matching ETH to account (`to`).
+    /// Emits {Transfer} event to reflect WETH10 token burn of `value` to `address(0)` from caller account.
+    /// Requirements:
+    ///   - caller account must have at least `value` balance of WETH10 token.
+    function withdrawTo(address payable to, uint256 value) external;
+}

pkg/sol/WETHRouter.sol

@@ -0,0 +1,41 @@
+// SPDX-Identifier: MIT
+
+pragma solidity 0.8.16;
+
+import "./ISeawaterAMM.sol";
+import "./IWETH10.sol";
+
+contract WETHRouter {
+    IWETH10 immutable WETH;
+    ISeawaterAMM immutable SEAWATER;
+
+    constructor(IWETH10 _weth, ISeawaterAMM _amm) {
+        WETH = _weth;
+        SEAWATER = _amm;
+    }
+
+    function swapIn32502CA71(
+        address _token,
+        uint256 _amount,
+        uint256 _minOut
+    ) external returns (int256, int256) {
+
+    }
+
+    function swapOut5E08A399(
+        address _token,
+        uint256 _amount,
+        uint256 _minOut
+    ) external returns (int256, int256) {
+
+    }
+
+    function swap2ExactInED91BB1D(
+        address _tokenA,
+        address _tokenB,
+        uint256 _amount,
+        uint256 _minOut
+    ) external returns (uint256, uint256) {
+
+    }
+}