v0.1.21

What's Changed

• chore: prep next release v0.1.21 by @github-actions[bot] in #73
• feat(nix): package the forge CLI as the flake's default package by @MarcusDunn in #74
• fix(oci): revalidate mutable tags against the registry by @MarcusDunn in #75

Full Changelog: v1...v0.1.21