Release 1.6.4

Either download the gog-downloader php binary below or use docker image rikudousage/gog-downloader:1.6.4.
If you're on Windows, you can also download the GogDownloaderSetup.exe installer.

What's Changed

• Chore: Update PHP version in the Windows setup by @RikudouSage in #19

Full Changelog: v1.6.3...v1.6.4