chore: fix coverage command

Author: Simon Renoult

package.json

@@ -20,7 +20,7 @@
   },
   "scripts": {
     "build": "rm -rf dist && tsc",
-    "coverage": "codecov",
+    "coverage": "nyc npm test",
     "lint": "eslint --ext .ts .",
     "prepare": "npm run lint && npm run build",
     "postversion": "git push --tags",