Split IP addresses range into address and prefix_len

I wrote a JSON schema validation for JAFAR in https://github.com/thibmeu/jafar.

One thing I noticed, which is similar in some other languages, is that there is a type for ipv4/ipv6, but none for the ip ranges. Something like

```
{
  "address": IPV4,
  "prefix_len": number,
}
```

I'm not sure to what extent this is prevalent, therefore opening an issue as a discussion point.