[svelte] Use GitHub environment in deployment

.github/workflows/deploy.yml

@@ -1,14 +1,15 @@
 name: Deploy
 on:
   push:
-    branches: [main, svelte]
+    branches: [ main, svelte ]
 env:
   FLY_API_TOKEN: ${{ secrets.FLY_API_TOKEN }}
 jobs:
   deploy:
     name: Deploy app
     runs-on: ubuntu-latest
     timeout-minutes: 10
+    environment: ${{ github.ref_name == 'production' && 'production' || 'beta' }}
     steps:
       - name: Checkout
         uses: actions/checkout@v4