chore: add NuGet v5.8 to publish

Author: madetara

appveyor.yml

@@ -16,7 +16,7 @@ after_build:
   - cd Cement.Net
   - if not exist ..\files-common\win10-x64 mkdir ..\files-common\win10-x64
   - dotnet publish -r win10-x64 -o ..\files-common\win10-x64 /p:PublishSingleFile=true /p:DebugType=None --self-contained true
-  - copy /Y ..\externals\NuGet.dll ..\files-common\win10-x64\NuGet.exe
+  - copy /Y ..\externals\NuGet.exe ..\files-common\win10-x64\NuGet.exe
   - if not exist ..\files-common\linux-x64 mkdir ..\files-common\linux-x64
   - dotnet publish -r linux-x64 -o ..\files-common\linux-x64 /p:PublishSingleFile=true /p:DebugType=None --self-contained true
   - if not exist ..\files-common\osx-x64 mkdir ..\files-common\osx-x64