[Feature request] Add logging level to logs

[yubiuser]

I'm using inadyn with the provided Docker image where it logs to stderr by default. I noticed that the logging level is not logged in this case, which I think could be a valuable additon.
E.g. from the log

inadyn[1]: In-a-dyn version 2.12.0 -- Dynamic DNS update client.
inadyn[1]: Guessing DDNS plugin '[email protected]' from 'cloudflare.com'

It's not clear that the second line has level "warning".

It could be improved as

inadyn[1]: INFO In-a-dyn version 2.12.0 -- Dynamic DNS update client.
inadyn[1]: WARN Guessing DDNS plugin '[email protected]' from 'cloudflare.com'