bindings/javascript: Add prepublish step

...hopefully sorts the missing native package problem.

bindings/javascript/package.json

@@ -35,9 +35,10 @@
     "artifacts": "napi artifacts",
     "build": "napi build --platform --release",
     "build:debug": "napi build --platform",
+    "prepublishOnly": "napi prepublish -t npm",
     "test": "ava",
     "universal": "napi universal",
     "version": "napi version"
   },
   "packageManager": "yarn@4.6.0"
-}
+}