Add cache to github actions

Author: beefoo

.github/workflows/deploy.yml

@@ -30,11 +30,11 @@ jobs:
       # if you have config:
       # execute:
       #   execute_notebooks: cache
-      # - name: cache executed notebooks
-      #   uses: actions/cache@v4
-      #   with:
-      #     path: _build/.jupyter_cache
-      #     key: jupyter-book-cache-${{ hashFiles('requirements.txt') }}
+      - name: cache executed notebooks
+        uses: actions/cache@v4
+        with:
+          path: _build/.jupyter_cache
+          key: jupyter-book-cache-${{ hashFiles('requirements.txt') }}
 
       # Build the book
       - name: Build the book