I was able to manually reference a local NETStandard library I wrote yesterday to test something. The script code is below. RefitTest.Client.dll is my library and I needed to reference netstandard.dll to get it to work. My client is simply implemented using the example at the top of http://paulcbetts.github.io/refit/

<Query Kind="Statements">
<Reference>C:\Projects\RefitTest\RefitTest.Console\RefitTest.Console.Framework\bin\Debug\netstandard.dll</Reference>
<Reference>C:\Projects\RefitTest\RefitTest.Client\bin\Debug\netstandard2.0\RefitTest.Client.dll</Reference>
<NuGetReference>Refit</NuGetReference>
<Namespace>Newtonsoft.Json</Namespace>
<Namespace>Refit</Namespace>
<Namespace>RefitTest.Client.GitHub</Namespace>
</Query>

var client = new GitHubClient();
var user = client.GetUserAsync("strandloper").GetAwaiter().GetResult();
Console.WriteLine(user.Name);