cidrSubnet('108.162.192.0/18').contains('::ffff:108.162.245.126') returns false

Not sure if this is normal but it caused me to waste some time:

using ^1.1.5:
```
const ip = require('ip')
console.log(ip.cidrSubnet('108.162.192.0/18').contains('::ffff:108.162.245.126')) // false
console.log(ip.cidrSubnet('108.162.192.0/18').contains('108.162.245.126')) // true
```

Reproduce the two cidrSubnet(...).contains(...) calls from the issue, then locate the cidrSubnet and contains implementation in the package. Check how IPv4-mapped IPv6 input is handled and determine the intended result; done should include behavior consistent with that decision and regression coverage for the shown case.

Written by the indexing model from the issue text.