Bump reviewdog/action-markdownlint from 0.14 to 0.20

Bumps [reviewdog/action-markdownlint](https://github.com/reviewdog/action-markdownlint) from 0.14 to 0.20.
- [Release notes](https://github.com/reviewdog/action-markdownlint/releases)
- [Commits](reviewdog/action-markdownlint@v0.14...v0.20)

---
updated-dependencies:
- dependency-name: reviewdog/action-markdownlint
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>

.github/workflows/reviewdog.yml

@@ -40,7 +40,7 @@ jobs:
           submodules: false
 
       - name: markdownlint
-        uses: reviewdog/action-markdownlint@v0.14
+        uses: reviewdog/action-markdownlint@v0.20
         with:
           reporter: github-pr-review
           fail_on_error: true