add remark about jwt

.env.example

@@ -41,5 +41,7 @@ EMAIL_SERVER_PASSWORD=email_password
 # Encryption key that will be used to encrypt CalDAV credentials, choose a random string, for example with `dd if=/dev/urandom bs=1K count=1 | md5sum`
 CALENDSO_ENCRYPTION_KEY=
 
+# It is highly recommended that the JWT secret must be overridden and very unique
 JWT_SECRET=secret
-NODE_ENV=production
+
+NODE_ENV=production