docs: fetch all branches and tags for multi-version building

Author: vpratz

.github/workflows/docs.yaml

@@ -19,8 +19,9 @@ jobs:
         uses: actions/checkout@v3
         with:
           path: dev
+          fetch-depth: 0
 
-      - name: Checkout gh-pages
+      - name: Checkout gh-pages-dev
         uses: actions/checkout@v3
         with:
           path: gh-pages-dev