Downgrade CI to nodejs 18

To ensure the scripts still work for people that haven't updated to v20 yet

.github/workflows/nodejs.yml

@@ -11,10 +11,10 @@ jobs:
         uses: actions/checkout@v3
         with:
           submodules: recursive
-      - name: Use Node.js 20.x
+      - name: Use Node.js 18.x
         uses: actions/setup-node@v3
         with:
-          node-version: 20.x
+          node-version: 18.x
       - name: Install testing dependencies
         run: npm ci
       - name: Test all apps and widgets