chore(deps): update actions/upload-pages-artifact action to v4 (#24)

This PR contains the following updates:

| Package | Type | Update | Change |
|---|---|---|---|
| [actions/upload-pages-artifact](https://github.com/actions/upload-pages-artifact) | action | major | `v3` -> `v4` |

---

### Release Notes

<details>
<summary>actions/upload-pages-artifact (actions/upload-pages-artifact)</summary>

### [`v4`](https://github.com/actions/upload-pages-artifact/compare/v3...v4)

[Compare Source](https://github.com/actions/upload-pages-artifact/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:eyJjcmVhdGVkSW5WZXIiOiI0MS45OC40IiwidXBkYXRlZEluVmVyIjoiNDEuOTguNCIsInRhcmdldEJyYW5jaCI6Im1haW4iLCJsYWJlbHMiOltdfQ==-->

Reviewed-on: #24
Co-authored-by: Renovate [BOT] <renovate-bot@git.tainton.uk>
Co-committed-by: Renovate [BOT] <renovate-bot@git.tainton.uk>

.github/workflows/pages.yml

@@ -29,11 +29,11 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout
-        uses: actions/checkout@v5
+        uses: actions/checkout@v4
       - name: Setup Pages
         uses: actions/configure-pages@v5
       - name: Upload artifact
-        uses: actions/upload-pages-artifact@v3
+        uses: actions/upload-pages-artifact@v4
         with:
           # Upload entire repository
           path: '.'