Add step to copy index.html to 404.html in deployment workflow

Author: miladsoft

.github/workflows/deploy.yml

@@ -24,6 +24,9 @@ jobs:
       - name: Build project
         run: yarn build
 
+      - name: Copy index.html to 404.html
+        run: cp build/index.html build/404.html
+
       - name: Deploy to GitHub Pages
         uses: peaceiris/actions-gh-pages@v4
         with: