Add install and cache steps

.github/workflows/deploy.yml

@@ -13,6 +13,24 @@ jobs:
       - uses: actions/setup-node@v4
         with:
           node-version: 20
+      - name: Cache node modules
+        id: cache-npm
+        uses: actions/cache@v3
+        env:
+          cache-name: cache-node-modules
+        with:
+          # npm cache files are stored in `~/.npm` on Linux/macOS
+          path: ~/.npm
+          key: ${{ runner.os }}-build-${{ env.cache-name }}-${{ hashFiles('**/package-lock.json') }}
+          restore-keys: |
+            ${{ runner.os }}-build-${{ env.cache-name }}-
+            ${{ runner.os }}-build-
+            ${{ runner.os }}-
+      - if: ${{ steps.cache-npm.outputs.cache-hit != 'true' }}
+        name: List the state of node modules
+        continue-on-error: true
+        run: npm list
+      - run: npm install
       - run: |
           npm run build
           rm -r build/api/posts build/api/posts.json