fix(npm): cache

Author: as-op

action.yml

@@ -32,11 +32,21 @@ runs:
         bundler-cache: true
         working-directory: ${{ github.action_path }}
 
+    # We need to copy md2pdfup's package-lock.json into the workspace
+    # because hashFiles only works on files inside the workspace.
+    - run: cp ${{ github.action_path }}/package-lock.json md2pdfup-package-lock.json
+      shell: bash
+
     - uses: actions/setup-node@v4
       with:
         node-version: "20.x"
         cache: "npm"
-        cache-dependency-path: "${{ github.action_path }}/package-lock.json"
+        cache-dependency-path: '**/md2pdfup-package-lock.json'
+
+    - uses: actions/cache@v4
+      with:
+        path: ${{ github.action_path }}/node_modules
+        key: md2pdfup-npm-${{ hashFiles('md2pdfup-package-lock.json') }}
 
     - run: |
         npm install