Add more parameters to the mDNS payload

[rneswold]

I've been building a Flutter app to interact with DrMem. It displays all the info obtained through the mDNS announcement. One thing that would be useful/interesting is how long the node has been up. This issue proposes a field should be added to the txt section that represents the start time of the node.

[rneswold]

There should be three fields added to the mDNS payload:

• The boot time of the node (maybe in an ISO format?)
• The version of the DrMem software
• A preferred connection address

Since the GraphQL schema can change from version to version, we can't assume the query to get the version will stay the same. Putting the version in the mDNS payload tells the app what to expect for the GraphQL schema.

The TOML file should have an option configuration item in the GraphQL section that specifies a preferred address to use when connecting. The mDNS discovery will return the address as seen on the local network. Someone, however, might use port forwarding in their router to reach their DrMem instance. With a dynamic DNS service, one could access DrMem outside their home. They would need to use this parameter so apps would know what address to use.