Update main.yml

Author: shenhuan2021

.github/workflows/main.yml

@@ -26,13 +26,14 @@ jobs:
           
       - name: Generate directory tree for doc
         run: |
-          tree doc -I '.git' > doc-tree.txt
+          tree doc -I '.git' > doc-tree.md
       
       - name: Merge Markdown files
         run: |
           touch combined.md
           cat doc/readme.md > combined.md
-          find doc -type f -name "*.md" ! -name "readme.md" | sort | xargs -I {} sh -c 'cat "$@" >> combined.md' _ {}
+          cat doc-tree.md > combined.md
+          find doc -type f -name "*.md" ! -name "readme.md" ！-name "doc-tree.md" | sort | xargs -I {} sh -c 'cat "$@" >> combined.md' _ {}
         
       - name: Convert README.md to README.pdf
         run: pandoc combined.md -o README.pdf --pdf-engine=xelatex