chore: bump DavidAnson/markdownlint-cli2-action from 20 to 21 (#98)

Bumps [DavidAnson/markdownlint-cli2-action](https://github.com/davidanson/markdownlint-cli2-action) from 20 to 21.
- [Release notes](https://github.com/davidanson/markdownlint-cli2-action/releases)
- [Commits](DavidAnson/markdownlint-cli2-action@v20...v21)

---
updated-dependencies:
- dependency-name: DavidAnson/markdownlint-cli2-action
  dependency-version: '21'
  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>
Co-authored-by: Manuel Doncel Martos <[email protected]>

Author: dependabot[bot]

.github/workflows/linters.yml

@@ -46,6 +46,6 @@ jobs:
     name: markdown
     runs-on: ubuntu-latest
     steps:
-      - uses: DavidAnson/markdownlint-cli2-action@v20
+      - uses: DavidAnson/markdownlint-cli2-action@v21
         with:
           globs: '**/*.md'