Develop unit test for mDNS-SD

[DazWilkin]

Rust SDK does not include unit test(s for mDNS Service Discovery).

SDK's mDNS crate (libmdns does not include a client browser.

Without a client to subscribe, it is difficult to prove service publication.

Alternatives would be to use avahi-browse --all and grep the results for _webthing._tcp?

Use an alternative mDNS crate .... but then, turtles...

[lu-zero]

I tested it with the mdns crate and it seems working.

[arpad-m]

A dev-dependency on mdns doesn't cause issues for downstream users. libmdns is a server and mdns is a client, so there is also no duplication. I think the question is more how to set up a dummy network that the two can talk to each other inside.