workflows: bump actions/checkout from 4 to 5 (fluent#2043)

Bumps [actions/checkout](https://github.com/actions/checkout) from 4 to 5.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v4...v5)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-version: '5'
  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>
Signed-off-by: Tom <[email protected]>

Author: dependabot[bot]

.github/workflows/pr-lint.yaml

@@ -8,7 +8,7 @@ jobs:
     runs-on: ubuntu-latest
     name: PR - Actionlint
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v5
       - run: |
           echo "::add-matcher::.github/actionlint-matcher.json"
           bash <(curl https://raw.githubusercontent.com/rhysd/actionlint/main/scripts/download-actionlint.bash)
@@ -19,14 +19,24 @@ jobs:
     runs-on: ubuntu-latest
     name: PR - Shellcheck
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v5
       - uses: ludeeus/action-shellcheck@master
 
+  markdownlint:
+    name: runner / markdownlint
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v5
+      - name: markdownlint
+        uses: prologic/[email protected]
+        with:
+          github_token: ${{ secrets.GITHUB_TOKEN }}
+          reporter: github-pr-review # Change reporter. (Only `github-pr-check` is supported at the moment).
   vale:
     name: runner / vale
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v5
       - uses: errata-ai/[email protected]
         with:
           files: all