Add udp appender

[pmnmq]

Add udp appender

• add udp appender
• self-testing has been completed.
• add example
• update readme

[nonconvextech]

Please fix the compilation issue. Thx.

[pmnmq]

Please fix the compilation issue. Thx.

I have fixed the compilation issue.

[pmnmq]

I have fixed the timeout issue that occurred during UDP testing. The cause was logging before the UDP service was successfully created.

[nonconvextech]

Could you add an option to allow users to serialize log message freely?
The current implementation is quite limited. What if we want to add some meta data before sending log messages?

[pmnmq]

Could you add an option to allow users to serialize log message freely? The current implementation is quite limited. What if we want to add some meta data before sending log messages?

Thank you for your reply!

I don't add too many options because I think the user should know how to find all the context-sensitive logs once the logs are ready to be collected.
Do you mean that you need to add some information to distinguish the logs of different services in the log server? Or generate JSON data for easy retrieval or analysis?