Allow specifying config file at runtime about swayblocks

[rei2hu]

Thanks for the suggestion!

An optional runtime argument to determine the path of the config file could be a possible solution, but I'm not sure if I'll make the update in a timely fashion because I don't run a *nix system anymore.

However, there might be one (hacky) way to do it with the current config file because it is actually just some code evaluated at runtime whose return value is used as the config.

A rough example would be something like this:

case System.get_env("DISPLAY") do
  # display 1
  "localhost:0.0" ->
    [
      %{
        :name => "display 1 config",
        :time => 1000,
      }
    ]
  # display 2
  "localhost:0.1" ->
    [
      %{
        :name => "display 2 config",
        :time => 2000,
      }
    ]
  # default case in case something messes up
  _unrecognized ->
    [
      %{
        :name => "default config",
        :time => 1000,
      }
    ]
end

(also there might be a weird quirk with accessing environment variables at runtime with Elixir that actually prevents this from working? But that code is evaluated at runtime so who knows)