nil in Variadic function

https://github.com/grandcat/zeroconf/blob/e1d6e579e89fc1ca9bb1faee9f2525065d3ca7d7/README.md?plain=1#L33resolver, err := 

```zeroconf.NewResolver(nil)``` 
should be 
```zeroconf.NewResolver()``` 
You don't need to pass nil, (and it should be error to pass nil).
