change workflow to use node-version 20

.github/workflows/main.yml

@@ -8,6 +8,10 @@ jobs:
     steps:
       - name: Checkout
         uses: actions/checkout@v4
+      - name: Setup Node.js
+        uses: actions/setup-node@v2
+        with:
+          node-version: "20.x"
       - uses: pnpm/action-setup@v2
       # Install npm dependencies, cache them correctly
       # and run all Cypress tests