Add "Source Port" to game type

Hi LB team,

In terms of Windows games, there are a lot of source ports/reimplementations and engine updates for old games that have come up over the years. I’m not sure the best game type to list them under; they really aren’t Homebrew because they often use original assets, and I think Unlicensed doesn’t work particularly well either. As more and more of these get released over the years, a Source Port category could be helpful to keep track of these new engines and updates that come out.

Thanks!