Add NODE_ENV=production to env sample

.env.sample

@@ -1,5 +1,7 @@
 # –––––––––––––––– REQUIRED ––––––––––––––––
 
+NODE_ENV=production
+
 # Generate a hex-encoded 32-byte random key. You should use `openssl rand -hex 32`
 # in your terminal to generate a random value.
 SECRET_KEY=generate_a_new_key