Add recursive submodules checkout during docs CI

.github/workflows/docs.yml

@@ -12,6 +12,8 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
+        with:
+          submodules: recursive
       - name: Set up environment
         uses: ./.github/actions/setup
       - run: bash scripts/git-user-config.sh