Bump DavidAnson/markdownlint-cli2-action from 16 to 19

Bumps [DavidAnson/markdownlint-cli2-action](https://github.com/davidanson/markdownlint-cli2-action) from 16 to 19.
- [Release notes](https://github.com/davidanson/markdownlint-cli2-action/releases)
- [Commits](DavidAnson/markdownlint-cli2-action@v16...v19)

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

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

.github/workflows/ci.yml

@@ -15,7 +15,7 @@ jobs:
       - name: Linting file references
         run: sys/lintrefs.sh
       - name: Linting markdown format
-        uses: DavidAnson/markdownlint-cli2-action@v16
+        uses: DavidAnson/markdownlint-cli2-action@v19
         with:
           config: src/.markdownlint.jsonc
           globs: src/**/*.md
@@ -26,7 +26,7 @@ jobs:
       - name: Build single markdown file
         run: make one
       - name: Linting single markdown format
-        uses: DavidAnson/markdownlint-cli2-action@v16
+        uses: DavidAnson/markdownlint-cli2-action@v19
         with:
           config: .one.markdownlint-cli2.jsonc
           globs: r2book.md