dart_skills_lint v0.4.0

• Fixed issue #166 by adding support for configuring individual skills via the individual_skills: key in dart_skills_lint.yaml, enabling path-specific rule severity mapping without relying on root directory scanning.
• Native binaries for macOS arm64, macOS x64, Linux x64, and Linux
  arm64 are now published to GitHub Releases. Install without the
  Dart SDK via curl -fsSL .../install.sh | bash, or download the
  tarball directly and verify its SHA256.
• macOS binaries are not yet code-signed; clear the
  quarantine flag with
  xattr -d com.apple.quarantine $(which dart_skills_lint) on
  first launch.
• The dart pub global activate dart_skills_lint and
  dev_dependencies: install paths are unchanged.