preserve struct

--standalone option to create a complete HTML document and the --toc option to generate a table of contents.

.github/workflows/md-html-deploy.yml

@@ -30,7 +30,7 @@ jobs:
         run: |
           mkdir -p _site
           for file in *.md; do
-            pandoc "$file" -o "_site/${file%.md}.html"
+            pandoc "$file" --standalone --toc -o "_site/${file%.md}.html"
           done
 
       - name: Deploy to GitHub Pages