Polyfill-data gem adds the Ruby 3.2 Data class to lower Ruby versions

I'm on a project that isn't yet on ruby 3.2 and wanted to use the new Data class. I implemented this to allow me to move to it easily.

It does still have 1 failing test about redefining the initialize method with a block, but it works for all other cases.

The Ruby 3.2 Data class is based on C code from Struct. This is all implemented with Ruby.