feat(contracts): Add contracts stub

contracts/HubPool.sol

@@ -0,0 +1,30 @@
+//SPDX-License-Identifier: Unlicense
+pragma solidity ^0.8.0;
+
+contract HubPool {
+    //   constructor() {}
+
+    function addLiquidity(address token, uint256 amount) public {}
+
+    function removeLiquidity(address token, uint256 amount) public {}
+
+    function exchangeRateCurrent(address token) public returns (uint256) {}
+
+    function liquidityUtilizationPostRelay(address token, uint256 relayedAmount) public returns (uint256) {}
+
+    function initiateRelayerRefund(
+        uint256[] memory bundleEvaluationBlockNumberForChain,
+        bytes32 chainBatchRepaymentProof,
+        bytes32 relayerRepaymentDistributionProof
+    ) public {}
+
+    function executeRelayerRefund(
+        uint256 relayerRefundRequestId,
+        uint256 leafId,
+        uint256 repaymentChainId,
+        address[] memory l1TokenAddress,
+        uint256[] memory accumulatedLpFees,
+        uint256[] memory netSendAmounts,
+        bytes32[] memory inclusionProof
+    ) public {}
+}

contracts/SpokePool.sol

@@ -0,0 +1,41 @@
+//SPDX-License-Identifier: Unlicense
+pragma solidity ^0.8.0;
+
+contract HubPool {
+    //   constructor() {}
+
+    function deposit(
+        address originToken,
+        uint256 amount,
+        address recipient,
+        uint256 destinationChainId,
+        uint256 relayerFee
+    ) public {}
+
+    function initiateRelay(
+        uint256 originChain,
+        address sender,
+        uint256 amount,
+        address recipient,
+        uint256 relayerFee,
+        uint256 realizedLpFee
+    ) public {}
+
+    function fillRelay(
+        uint256 relayId,
+        uint256 fillAmount,
+        uint256 repaymentChain
+    ) public {}
+
+    function initializeRelayerRefund(bytes32 relayerRepaymentDistributionProof) public {}
+
+    function distributeRelayerRefund(
+        uint256 relayerRefundId,
+        uint256 leafId,
+        address l2TokenAddress,
+        uint256 netSendAmount,
+        address[] memory relayerRefundAddresses,
+        uint256[] memory relayerRefundAmounts,
+        bytes32[] memory inclusionProof
+    ) public {}
+}