Update BOT Token during execution

I have included a function to update the Token during execution time so the token can be stored in (for example) the EEPROM and retrieved during setup.

Author: rafaelcbarbosa

src/UniversalTelegramBot.h

@@ -49,6 +49,7 @@ struct telegramMessage {
 class UniversalTelegramBot {
 public:
   UniversalTelegramBot(String token, Client &client);
+  void updateToken(String token);
   String sendGetToTelegram(String command);
   String sendPostToTelegram(String command, JsonObject &payload);
   String