Fix broken test in connection.ts for node 18 and add node 18 testing (#2183)

* Change localhost to 127.0.0.1

* Add Node 18 testing

packages/xrpl/test/connection.test.ts

@@ -136,7 +136,7 @@ describe('Connection', function () {
     createServer().then((server: net.Server) => {
       const port = (server.address() as net.AddressInfo).port
       const options = {
-        proxy: `ws://localhost:${port}`,
+        proxy: `ws://127.0.0.1:${port}`,
         authorization: 'authorization',
         trustedCertificates: ['path/to/pem'],
       }