fix docs: specify lock file for caching

Author: JohnnyCrazy

.github/workflows/docs.yaml

@@ -19,6 +19,8 @@ jobs:
         with:
           node-version: v20.9.0
           cache: "pnpm"
+          cache-dependency-path: |
+            SpotifyAPI.Docs/pnpm-lock.yaml
       - name: Setup GitHub Deploy SSH Key
         uses: webfactory/[email protected]
         with: