build: bump @junobuild/vite-plugin from 0.0.19 to 3.4.0 in /demo

Bumps [@junobuild/vite-plugin](https://github.com/junobuild/plugins/tree/HEAD/plugins/vite-plugin) from 0.0.19 to 3.4.0.
- [Release notes](https://github.com/junobuild/plugins/releases)
- [Commits](https://github.com/junobuild/plugins/commits/v3.4.0/plugins/vite-plugin)

---
updated-dependencies:
- dependency-name: "@junobuild/vite-plugin"
  dependency-version: 3.4.0
  dependency-type: direct:development
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

demo/package-lock.json

@@ -13,7 +13,7 @@
   },
   "devDependencies": {
     "@junobuild/config": "^0.1.1",
-    "@junobuild/vite-plugin": "^0.0.19",
+    "@junobuild/vite-plugin": "^3.4.0",
     "@tailwindcss/vite": "^4.0.6",
     "autoprefixer": "^10.4.20",
     "prettier": "^3.5.1",