Add support for mDNS

[proddy]

We had this in v2. Use the ESPmDNS.h library, do a MDNS.begin() using the hostname and add the TCP services for the Web server. Maybe it'll help with EMS-ESP not setting the hostname correctly on some older routers.

https://docs.espressif.com/projects/esp-idf/en/latest/esp32/api-reference/protocols/mdns.html

[proddy]

registered the http and telnet services and included some text. I used esphome as an example. Also disabled the OTAService from doing the same thing. Now EMS-ESP should be discoverable on ems-esp.local and maybe it resolves some of the DNS names on some older routers. In build v3.2.2b13

[proddy]

confirmed working (via Discord)