Bump DavidAnson/markdownlint-cli2-action from 19 to 20

Bumps [DavidAnson/markdownlint-cli2-action](https://github.com/davidanson/markdownlint-cli2-action) from 19 to 20.
- [Release notes](https://github.com/davidanson/markdownlint-cli2-action/releases)
- [Commits](DavidAnson/markdownlint-cli2-action@v19...v20)

---
updated-dependencies:
- dependency-name: DavidAnson/markdownlint-cli2-action
  dependency-version: '20'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

.github/workflows/markdown.yml

@@ -19,7 +19,7 @@ jobs:
       - name: Checkout
         uses: actions/checkout@v4
       - name: Run markdownlint
-        uses: DavidAnson/markdownlint-cli2-action@v19
+        uses: DavidAnson/markdownlint-cli2-action@v20
         with:
           fix: true
           globs: "**/*.md"