Some simple readme

[dselivanov]

Hi Simon. Thanks for great package (as usual).

Would be great to have simple readme which can help less experienced users:

• example on how to use reference ulogd implementations (for me was not that obvious)
• mention standard system loggers like rsyslog, syslog-ng, nxlog. For example I found this introduction article quite useful - https://sematext.com/blog/what-is-syslog-daemons-message-formats-and-protocols/
• may be example on how to use ulog with rsyslog

If you are interested, I can send PR.

[s-u]

I agree that it would be useful. If you have a minute for a PR, that would be great.