Update gh-pages.yml

Author: hweifluids

.github/workflows/gh-pages.yml

@@ -17,6 +17,11 @@ jobs:
         with:
           fetch-depth: 0
 
+      - name: Install system dependencies
+        run: |
+          sudo apt-get update
+          sudo apt-get install -y doxygen
+
       - name: Set up Python
         uses: actions/setup-python@v4
         with: