Bump DavidAnson/markdownlint-cli2-action from 13 to 15 (#58)

Bumps [DavidAnson/markdownlint-cli2-action](https://github.com/davidanson/markdownlint-cli2-action) from 13 to 15.
- [Release notes](https://github.com/davidanson/markdownlint-cli2-action/releases)
- [Commits](DavidAnson/markdownlint-cli2-action@v13...v15)

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

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

.github/workflows/lint_md_all.yml

@@ -8,7 +8,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
     - uses: actions/checkout@v4
-    - uses: DavidAnson/markdownlint-cli2-action@v13
+    - uses: DavidAnson/markdownlint-cli2-action@v15
       with:
         globs: |
           *.md

.github/workflows/lint_md_changes.yml

@@ -21,7 +21,7 @@ jobs:
       with:
         files: '**/*.md'
         separator: ","
-    - uses: DavidAnson/markdownlint-cli2-action@v13
+    - uses: DavidAnson/markdownlint-cli2-action@v15
       if: steps.changed-files.outputs.any_changed == 'true'
       with:
         globs: ${{ steps.changed-files.outputs.all_changed_files }}