[Tests] add aud in posttest

Author: ljharb

package.json

@@ -9,6 +9,7 @@
   },
   "bugs": "https://github.com/substack/node-shell-quote/issues",
   "devDependencies": {
+    "aud": "^2.0.1",
     "tape": "^5.6.1"
   },
   "homepage": "https://github.com/substack/node-shell-quote",
@@ -26,6 +27,7 @@
   },
   "scripts": {
     "tests-only": "tape 'test/**/*.js'",
-    "test": "npm run tests-only"
+    "test": "npm run tests-only",
+    "posttest": "aud --production"
   }
 }