DotNetCore NSIS macro

FYI there are header files to check latest version of dotnet versions.
Original creator, danpaul88: https://github.com/danpaul88/nsis-dotnetcore
jglk added win 7 support: https://github.com/jglk/nsis-dotnetcore
more complete version by jpk6789: https://github.com/jpk6789/nsis-dotnetcore
Header files are in src folder.