use regex on url to accept .png
hi,

I have an endpoint that returns an image. I want to check on my router if is being passed the id or id.png.

I have been tried the example below:

```
router.get(
  '/api/image/:paymentLinkID(.png)?',
  getImageFunction,
);
```

but, returns `not found` for me.

What is the correct way to do this?