always make site directory

Author: peterdroberts

.github/workflows/ci.yml

@@ -13,6 +13,7 @@ jobs:
       - uses: actions/setup-python@v2
         with:
           python-version: 3.x
+      - run: mkdir -p site
       - run: pip install mkdocs
       - run: pip install mkdocs-material
       - run: pip install mkdocs-video