Monitoring UI Listening Address

[ups7]

Hello,

Thank you for providing this Docker image. I got dnscrypt-proxy working on my setup. I would like to suggest a small improvement.

The example config file included has the listening address for the monitoring UI as
listen_address = "127.0.0.1:8080"

That didn't work for me on Docker, but it started working when I changed it to:
listen_address = "0.0.0.0:8080"

If you agree, please update this in the default file.

Thanks!