use dotnet nuget

Author: isc30

.github/workflows/release-beta.yml

@@ -60,7 +60,7 @@ jobs:
       run: dotnet nuget push output/nuget/**/*.nupkg --api-key ${{ secrets.NUGET_API_KEY }} --source https://api.nuget.org/v3/index.json --skip-duplicate
 
     - name: Add GitHub NuGet Source
-      run: nuget sources add -name "github" -Source https://nuget.pkg.github.com/isc30/index.json -Username isc30 -Password ${{ secrets.GITHUB_TOKEN }}
+      run: dotnet nuget add source https://nuget.pkg.github.com/isc30/index.json --name "github" --username isc30 --password ${{ secrets.GITHUB_TOKEN }}
 
     - name: Push package to GitHub
       run: dotnet nuget push output/nuget/**/*.nupkg --source "github" --skip-duplicate