Hi, I'm trying to figure out if something is missing from the documentation or if I should create a feature request.

1. Listen on multiple IPs and ports

#1083 I guess.

I want to configure slskd to listen on IPv4 and IPv6, on localhost and VPN, how can I do that?
Consider the following examples

1. • [::]:5030
   • 0.0.0.0:5030
2. • 127.0.0.1:5030
   • 192.168.0.1:5030
3. • [::1]:5030
   • 127.0.0.1:5030
   • 192.168.0.1:5030

2. Dedicated port for Prometheus metrics

#1108

I think it's common industry practice to make a separate port for Prometheus so it doesn't interfere with the rest of the application. Currently, I think Prometheus occupies the /metrics path on the default http server port.

3. Client certificate auth

#1109

Some of the Prometheus metrics exporters support authentication using client certificates. I don't think slskd supports this feature.

4. Soulseek port in Docker

#1110

If I export port 8000 using Docker, do I need to change the port from 50300 to 8000?

services:
  slskd:
    ports:
      - "8000:50300"
  environment:
    SLSKD_SLSK_LISTEN_PORT: "50300"

5. Yaml config in a single environment variable

#1111

I don't know if it's practical or not, but I would like to see an environment variable that could be interpreted as a config file, like gitlab omnibus does with its GITLAB_OMNIBUS_CONFIG variable.
This feature is needed because docker-compose doesn't support uploading config to the remote server without building the container in-place or using docker swarm.

6. Default value in docs/config.md

#1110

It would be very helpful to have an additional table column with the default value for each config option.
https://github.com/slskd/slskd/blob/ed4a4268d810a844657adde2d32865f11159eb3c/docs/config.md

7. Meaning of the ~ symbol in docs/config.md

#1110

I don't understand the meaning of ~ as an option value. I assume it's a default.