deps: eslint-formatter-unix

Problem:

    $ eslint --format=unix .
    The unix formatter is no longer part of core ESLint. Install it
    manually with `npm install -D eslint-formatter-unix`

Solution:
Install `eslint-formatter-unix`.

Author: justinmk

package-lock.json

@@ -16,6 +16,7 @@
     "@typescript-eslint/parser": "^8.41.0",
     "eslint": "^9.34.0",
     "eslint-config-prettier": "^10.1.8",
+    "eslint-formatter-unix": "^8.40.0",
     "eslint-plugin-import": "^2.32.0",
     "eslint-plugin-unicorn": "^60.0.0",
     "husky": "^9.1.7",