Add UUPS support

packages/core/contracts/import.sol

@@ -0,0 +1,11 @@
+// SPDX-License-Identifier: MIT
+pragma solidity ^0.8.0;
+
+import "@openzeppelin/contracts/proxy/ERC1967/ERC1967Proxy.sol";
+import "@openzeppelin/contracts/proxy/transparent/TransparentUpgradeableProxy.sol";
+import "@openzeppelin/contracts/proxy/transparent/ProxyAdmin.sol";
+
+// Kept for backwards compatibility with older versions of Hardhat and Truffle plugins.
+contract AdminUpgradeabilityProxy is TransparentUpgradeableProxy {
+    constructor(address logic, address admin, bytes memory data) payable TransparentUpgradeableProxy(logic, admin, data) {}
+}