ci: run actions/setup-node before npm publish

Otherwise it does not try to use NODE_AUTH_TOKEN.

.github/workflows/deltachat-rpc-server.yml

@@ -390,6 +390,12 @@ jobs:
             --repo ${{ github.repository }} \
             deltachat-rpc-server/npm-package/*.tgz
 
+      # Configure Node.js for publishing.
+      - uses: actions/setup-node@v4
+        with:
+          node-version: 20
+          registry-url: "https://registry.npmjs.org"
+
       - name: Publish npm packets for prebuilds and `@deltachat/stdio-rpc-server`
         if: github.event_name == 'release'
         working-directory: deltachat-rpc-server/npm-package