Update actions/setup-node action to v6 (#43)

This PR contains the following updates:

| Package | Type | Update | Change |
|---|---|---|---|
| [actions/setup-node](https://github.com/actions/setup-node) | action | major | `v3` -> `v6` |

---

### Release Notes

<details>
<summary>actions/setup-node (actions/setup-node)</summary>

### [`v6`](https://github.com/actions/setup-node/compare/v5...v6)

[Compare Source](https://github.com/actions/setup-node/compare/v5...v6)

### [`v5`](https://github.com/actions/setup-node/compare/v4...v5)

[Compare Source](https://github.com/actions/setup-node/compare/v4...v5)

### [`v4`](https://github.com/actions/setup-node/compare/v3...v4)

[Compare Source](https://github.com/actions/setup-node/compare/v3...v4)

</details>

---

### Configuration

📅 **Schedule**: Branch creation - At any time (no schedule defined), Automerge - At any time (no schedule defined).

🚦 **Automerge**: Disabled by config. Please merge this manually once you are satisfied.

♻ **Rebasing**: Whenever PR becomes conflicted, or you tick the rebase/retry checkbox.

🔕 **Ignore**: Close this PR and you won't be reminded about this update again.

---

 - [ ] <!-- rebase-check -->If you want to rebase/retry this PR, check this box

---

This PR has been generated by [Renovate Bot](https://github.com/renovatebot/renovate).
<!--renovate-debug:eyJjcmVhdGVkSW5WZXIiOiI0MS4xNTIuMiIsInVwZGF0ZWRJblZlciI6IjQxLjE1Mi4yIiwidGFyZ2V0QnJhbmNoIjoibmV4dCIsImxhYmVscyI6W119-->

Reviewed-on: #43
Co-authored-by: Renovate Bot <renovate-bot@valverde.cloud>
Co-committed-by: Renovate Bot <renovate-bot@valverde.cloud>

packages/webapp/public/98.css/.github/workflows/npm-publish.yml

@@ -13,7 +13,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v5
-      - uses: actions/setup-node@v3
+      - uses: actions/setup-node@v6
         with:
           node-version: 16
           registry-url: https://registry.npmjs.org/