sign method
Generate a signature needed for the WebSocket authentication as defined here: https://bybit-exchange.github.io/docs/inverse/?console#t-websocketauthentication
Implementation
String sign({required String secret, required int timestamp}) {
var msg = utf8.encode('GET/realtime' + timestamp.toString());
var key = utf8.encode(secret);
var hmac = Hmac(sha256, key);
return hmac.convert(msg).toString();
}