GH Actions: upgrade to Node.js 20 (was 16)

Author: generalmimon

.github/workflows/main.yml

@@ -14,7 +14,7 @@ jobs:
           submodules: true
       - uses: actions/setup-node@v4
         with:
-          node-version: 16
+          node-version: '20'
       - run: npm ci
       - run: npm run build
       - name: Deploy