fix: include \r? when verifying 'dotnet nuget'

When running the plugin on Windows, the validation of 'dotnet nuget' fails because Windows uses \r\n for newlines.

To fix this, \r? is included in the regular expression that splits the output from the dotnet nuget --version command.

Inspired by this article: https://bobbyhadz.com/blog/javascript-split-string-by-newline#split-a-string-by-newline-in-javascript