Exposing winston logger for use in other packages

[yardz]

I wish I could use the same logger in other packages (e.g: https://github.com/minddocdev/nest-express-winston), but currently the logger is private and there is no way to access it.

To use it I need to access the same Logger object, but it is currently private. I noticed that the createNestWinstonLogger function just creates an object so I just added a function to export the Logger.

After that, it is possible to use the same logger in other midwares or packages.

const logger = WinstonModule.createLogger({/*... No changes here ...*/ });
const configs: NestApplicationOptions = {logger};
const app = await NestFactory.create(AppModule, {logger});

// adding logger in another function 
const expressWinstonHandler = createExpressWinstonHandler(logger.getWinstonLogger());
app.use(expressWinstonHandler);
// ...