[Enhancement] Make Invidious listen dual stack ipv4 and ipv6

[unixfox]

Is your enhancement request related to a problem? Please describe.
By default, invidious does not listen on IPv6.

Describe the solution you'd like
I would like to have invidious listening on ipv4 and ipv6 at the same time.

Describe alternatives you've considered

Additional context
Related to #4693

[unixfox]

Forcing Kemal.config.host_binding to :: works for Linux but not FreeBSD, see here: #4693 (comment)

I'm not sure how to tackle this improvement. Maybe we should have an if case for BSD distributions in order to not listen on ::.

[GlowingUmbreon]

It may be possible to just add a note to the documentation that mentions that invidious listens to a IPv6 address and you will need to either set the address manually or to enable the IPv4 address or set the IPv4, IPv6 translation on your operating system based on requirements.
It appears that most Linux distros should work out of the box, if you are on a operating system or Distro that does does not have this feature enabled by default it is likely you are already comfortable with making changes to the config to get this working.

The main concern I have with this is breaking user's existing configurations. If any invidious instance maintainers rely on listening to IPv4 and the default changes without warning this could potentially be a problem. I know my configuration is currently susceptible to this.

[SamantazFox]

Listening on both is possible, the stdlib supports dual stack:

require "http/server"

server = HTTP::Server.new { }
server.bind_tcp("127.0.0.1", 10080)
server.bind_tcp("::1", 10080)

server.each_address do |addr|
  pp addr
end

# output
Socket::IPAddress(127.0.0.1:10080)
Socket::IPAddress([::1]:10080)

But we need to open a pull request for kemal, as it only supports binding to a single IP:
https://github.com/kemalcr/kemal/blob/5554d3d2f1b7496e850df48663c48765aa8af511/src/kemal.cr#L51-L61

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Edit: I realized that we could create our own HTTP::Server, store it in Kemal.config.server and then call Kemal.run, though.