Upload the NuGet package artifact

So that we can get it in subsequent jobs (publish-release and publish-prerelease)

Author: 0xced

.github/workflows/continuous-integration.yml

@@ -28,6 +28,9 @@ jobs:
       - run: dotnet test --no-build --verbosity normal
       - run: dotnet pack --no-build --verbosity normal
         id: dotnet-pack
+      - uses: actions/upload-artifact@v2
+        with:
+          path: "**/*.nupkg"
   publish-release:
     runs-on: macos-latest
     needs: package