gzN creates Folgezettel, gzn should work on visual

The description of `gzN` does not say that a Folgezettel link will be created:
```
creates a new zettel using the current word under the cursor as its title. 
```
However since other commands with a capital letter also create Folgezettels, I think this is the correct behavior and should be documented. Would it be possible to add the same functionality to `gzn`?