Updated converter for complex data

[scorovit]

For example:

{
"user": {
"first_name": "Name1",
"last_name": "Name2"
}
}

getJSONValue(named: "user.first_name", from: values, defaultValue: nil)
getJSONValue(named: "user.last_name", from: values, defaultValue: nil, separator: ".")

[CLAassistant]

Thank you for your submission, we really appreciate it. Like many open source projects, we ask that you all sign our Contributor License Agreement before we can accept your contribution.
3 out of 4 committers have signed the CLA.

✅ rymcol
✅ scorovit
✅ kjessup
❌ iamjono
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