make sure github actions pulls submodules

Author: thrau

Diff for: .github/workflows/github-pages.yml

@@ -13,6 +13,8 @@ jobs:
     runs-on: ubuntu-18.04
     steps:
       - uses: actions/checkout@v2
+        with:
+          submodules: recursive
 
       - name: Setup Hugo
         uses: peaceiris/actions-hugo@v2