Align the markdown workflow with the others (#3570)

Checkout package-lock.json from main and use node v20.
Add --yes to npx because it seems to need it when run locally,
although it's probably redundant in the CI environment.  But
it's safe to include.

Author: handrews

.github/workflows/validate-markdown.yaml

@@ -23,10 +23,10 @@ jobs:
         fetch-depth: 0
     - name: use the javascript environment from main
       run: |
-        git checkout remotes/origin/main -- package.json
+        git checkout remotes/origin/main -- package.json package-lock.json
     - uses: actions/setup-node@v4 # setup Node.js
       with:
-        node-version: '14.x'
+        node-version: '20.x'
     - name: Validate markdown
-      run: npx mdv versions/3.*.md
+      run: npx --yes mdv versions/3.*.md