Adds prepare script to install fork correctly

Author: zwergius

examples/sveltekit-js/package.json

@@ -5,6 +5,7 @@
     "dev": "svelte-kit dev",
     "build": "svelte-kit build",
     "package": "svelte-kit package",
+    "prepare": "npm run build",
     "preview": "svelte-kit preview",
     "lint": "prettier --ignore-path .gitignore --check --plugin-search-dir=. . && eslint --ignore-path .gitignore .",
     "format": "prettier --ignore-path .gitignore --write --plugin-search-dir=. ."