Bump actions/checkout from 3 to 4 (#5)

Bumps [actions/checkout](https://github.com/actions/checkout) from 3 to 4.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v3...v4)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

.github/workflows/gh-pages.yaml

@@ -10,14 +10,14 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout source
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
         with:
           ref: master
           fetch-depth: '0'
           path: 'source'
 
       - name: Checkout dist
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
         with:
           ref: gh-pages
           fetch-depth: '0'