Update file platform to be netcore for Windows 8 NuGet package.
Update file platform to be netcore for Windows 8 NuGet package.

netonjm/CocosSharp,zmaruo/CocosSharp,netonjm/CocosSharp,mono/CocosSharp,mono/CocosSharp,MSylvia/CocosSharp,hig-ag/CocosSharp,zmaruo/CocosSharp,hig-ag/CocosSharp,TukekeSoft/CocosSharp,TukekeSoft/CocosSharp,haithemaraissia/CocosSharp,MSylvia/CocosSharp,haithemaraissia/CocosSharp