Add rebalancing warp route extensions

solidity/contracts/token/extensions/HypERC20RebalancingCollateral.sol

@@ -0,0 +1,37 @@
+// SPDX-License-Identifier: Apache-2.0
+pragma solidity >=0.8.0;
+
+import {HypERC20Collateral} from "../HypERC20Collateral.sol";
+
+/**
+ * @title Hyperlane Rebalancing Token Collateral
+ * @author Abacus Works
+ */
+contract HypERC20RebalancingCollateral is HypERC20Collateral {
+    HypERC20Collateral public immutable rebalancer;
+
+    constructor(
+        address _erc20,
+        address _mailbox,
+        address _rebalancer
+    ) HypERC20Collateral(_erc20, _mailbox) {
+        rebalancer = HypERC20Collateral(_rebalancer);
+        require(
+            rebalancer.wrappedToken() == wrappedToken,
+            "Rebalancer collateral must match wrapped token"
+        );
+    }
+
+    function transferCollateral(
+        uint32 destination,
+        uint256 amount
+    ) external payable onlyOwner {
+        bytes32 router = _mustHaveRemoteRouter(destination);
+        require(wrappedToken.approve(address(rebalancer), amount));
+        rebalancer.transferRemote{value: msg.value}(
+            destination,
+            router,
+            amount
+        );
+    }
+}

solidity/contracts/token/extensions/HypNativeRebalancing.sol

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+// SPDX-License-Identifier: Apache-2.0
+pragma solidity >=0.8.0;
+
+import {HypNative} from "../HypNative.sol";
+
+/**
+ * @title Hyperlane Rebalancing Native Collateral
+ * @author Abacus Works
+ */
+contract HypERC20RebalancingCollateral is HypNative {
+    HypNative public immutable rebalancer;
+
+    constructor(
+        address _mailbox,
+        address payable _rebalancer
+    ) HypNative(_mailbox) {
+        rebalancer = HypNative(_rebalancer);
+    }
+
+    function transferCollateral(
+        uint32 destination,
+        uint256 amount
+    ) external payable onlyOwner {
+        bytes32 router = _mustHaveRemoteRouter(destination);
+        uint256 payment = msg.value + amount;
+        require(address(this).balance >= payment, "Insufficient balance");
+        rebalancer.transferRemote{value: payment}(destination, router, amount);
+    }
+}