Does not announce services without a Service Type Enumeration query first

[CaptChrisD]

Describe the bug
The PTR records are not announced for services unless a Service Type Enumeration query (_services._dns-sd._udp.local) is sent on the network.

To Reproduce
Steps to reproduce the behavior:
Start MdnsLite with services defined BUT no devices on the network that will conduct a Service Type Enumeration.

Expected behavior
When MdnsLite starts and an address is acquired for the interface the service announcement should be conducted.

[fhunleth]

The mDNS RFC does provide some guidance for announcements in https://www.rfc-editor.org/rfc/rfc6762#section-8.3. A PR that implements the startup announcement would be appreciated. I'm not sure that this fixes your issue, but it seems like it would help.

[CaptChrisD]

From what I can see there is no unsolicited announcement, correct?

Also, I have looked through the code some and it is not clear where this may get added. If you could offer a couple of suggestions I am happy to take a look at making a PR.