The WebView2 crate build pipeline requires NuGet to have a PackageSource to install the Microsoft.Web.WebView2 package. If you never used NuGet before, you might need to create a file named NuGet.Config on %APPDATA%/NuGet folder, with the following contents:
<?xml version="1.0" encoding="utf-8"?>
<configuration>
<packageSources>
<add key="nuget.org" value="https://api.nuget.org/v3/index.json" protocolVersion="3" />
</packageSources>
</configuration>
This configuration enables the default NuGet registry.