Update actions/checkout action to v4 (#5)

This PR contains the following updates:

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

---

### Release Notes

<details>
<summary>actions/checkout (actions/checkout)</summary>

###
[`v4`](https://redirect.github.com/actions/checkout/blob/HEAD/CHANGELOG.md#v417)

[Compare
Source](https://redirect.github.com/actions/checkout/compare/v3...v4)

- Bump the minor-npm-dependencies group across 1 directory with 4
updates by [@&#8203;dependabot](https://redirect.github.com/dependabot)
in
[https://github.com/actions/checkout/pull/1739](https://redirect.github.com/actions/checkout/pull/1739)
- Bump actions/checkout from 3 to 4 by
[@&#8203;dependabot](https://redirect.github.com/dependabot) in
[https://github.com/actions/checkout/pull/1697](https://redirect.github.com/actions/checkout/pull/1697)
- Check out other refs/\* by commit by
[@&#8203;orhantoy](https://redirect.github.com/orhantoy) in
[https://github.com/actions/checkout/pull/1774](https://redirect.github.com/actions/checkout/pull/1774)
- Pin actions/checkout's own workflows to a known, good, stable version.
by [@&#8203;jww3](https://redirect.github.com/jww3) in
[https://github.com/actions/checkout/pull/1776](https://redirect.github.com/actions/checkout/pull/1776)

</details>

---

### Configuration

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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

---

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.github/workflows/shellcheck.yaml

@@ -8,7 +8,7 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - name: "Run shellcheck"
         uses: ludeeus/action-shellcheck@master
         with: