v0.19.0

This release includes a couple of improvements:

1. On all targets, we bundle the default Nix version we install into the installer binary itself.
2. On macOS, we give a better error message when a device policy would prevent mounting the internal Nix Store volume we want to create.

What's Changed

• Embedding the Nix installer in the binary. by @grahamc in #897
• Error on SUIS by @grahamc in #941

Full Changelog: v0.18.0...v0.19.0