Add FetchCode support for nuget

[TG1999]

PURL: pkg:nuget/Newtonsoft.Json@13.0.1

Download URL:
https://www.nuget.org/api/v2/package/Newtonsoft.Json/13.0.1

[TG1999]

This is done in

https://github.com/package-url/packageurl-python/blob/main/src/packageurl/contrib/purl2url.py#L425

Commit:

package-url/packageurl-python@9ea1cea