Add mDNS update to main loop for ESP8266

[shmick]

On ESP8266 it needs MDNS.update() to run in the main loop

[prampec]

As far as I see, the update must be called as frequently as possible in ESP8266.
https://github.com/esp8266/Arduino/blob/master/libraries/ESP8266mDNS/src/LEAmDNS.h

So it should be placed inside the doLoop() method. (Must be tested before I approve!)

[shmick]

So it should be placed inside the doLoop() method. (Must be tested before I approve!)

My code update does place it inside doLoop() inside of the else if (this->_state == OnLine statement

I can confirm that it's working from my own local testing. Always best to have others test as well.

[prampec]

Sorry, I have missed something.

[prampec]

Thank you for your contribution.