feat: add initialization event for ERC20TransferModule and update tests

Author: YukiTsuchida

src/example/ERC20TransferModule.sol

@@ -17,6 +17,8 @@ abstract contract ERC20TransferModule is Initializable, ContractModuleBase, Owna
     error ERC20TransferModuleNotInitialized();
     error ERC20TransferModuleInvalidAddress();
 
+    event ERC20TransferModuleInitialized(address indexed crossModule, address indexed token);
+
     struct PendingTx {
         address from;
         address to;
@@ -43,6 +45,8 @@ abstract contract ERC20TransferModule is Initializable, ContractModuleBase, Owna
         }
         crossModule = _crossModule;
         token = IERC20(_token);
+
+        emit ERC20TransferModuleInitialized(_crossModule, _token);
     }
 
     function decodeCallInfo(bytes calldata callInfo)

test/ERC20TransferModule.t.sol

@@ -82,8 +82,8 @@ contract ERC20ModuleTest is Test {
         address crossModule = makeAddr("newCrossModule");
         address newToken = makeAddr("newToken");
 
-        assertEq(newHarness.crossModule(), address(0));
-        assertEq(address(newHarness.token()), address(0));
+        vm.expectEmit(address(newHarness));
+        emit ERC20TransferModule.ERC20TransferModuleInitialized(crossModule, newToken);
 
         newHarness.initialize(crossModule, newToken);