ci: Apply changes by Copilot's code review

Author: utilForever

.github/workflows/docs.yml

@@ -3,6 +3,8 @@ name: Document
 on:
   push:
     branches: [ main ]
+  pull_request:
+    branches: [ main ]
 
 jobs:
   build-docs:
@@ -11,7 +13,7 @@ jobs:
     steps:
     - uses: actions/checkout@v4
       with:
-        recursive: "recursive"
+        submodules: recursive
     - name: Installation
       run: sudo apt-get -y install ps2eps texlive-latex-extra doxygen
     - name: Build