Doc - call Realm.close in Node.js examples

When trying a Node.js example https://realm.io/docs/javascript/latest/#getting-started the process hangs because it has opened a handle. The realm has to be closed: realm.close().

Similarly, the NodeInterprocess listener.js example is not correct. It works just because the opened handle prevents the process to close. A correct program should catch a signal (Ctrl+C, keypress, …) and to proper close/clean up. Similarly for the winston-realm.js.

Have not checked the other examples, but you should always make proper close when you do open in examples.