Add support for RL v2.38

[tfausak]

Fixes #296.

Also this will change the shape of release assets in three ways:

• Rather than a binary, the asset will be a *.tar.gz file. When unpacked, it will contain only the executable. This makes it so that the executable bit stays set. In other words, you don't need to do chmod +x.
• A binary will be added for the ARM64 architecture on macOS. This supports Apple Silicon.
• The name of the assets will change. For example previously there was rattletrap-12.1.3-macos but now that would be rattletrap-12.1.3-darwin-x64.tar.gz. In general the assets will be named rattletrap-VER-OS-ARCH.tar.gz.

[tfausak]

Oh, also the executable won't be compressed with UPX anymore.