Add runtime support: don't only listen on /tmp/frajtano1, script to add peer

lib/agent.ex

@@ -49,6 +49,7 @@ defmodule Frajtano.Agent do
 
   @impl true
   def handle_call({:add_peer, path}, _from, state) do
+    # TODO: deduplicate peers by socket path
     case Peer.start(path) do
       {:ok, _} -> {:reply, :ok, state}
       {:error, error} -> {:reply, {:error, error}, state}

lib/frajtano.ex

@@ -18,7 +18,7 @@ defmodule Frajtano.Supervisor do
   def init(:ok) do
   	children = [
   	  Frajtano.Agent,
-  	  {Frajtano.Listener, ["/tmp/frajtano1"]},
+  	  {Frajtano.Listener, [Application.fetch_env!(:frajtano, :listen_path)]},
   	  {Task.Supervisor, name: Frajtano.ClientSupervisor},
   	  {DynamicSupervisor, name: Frajtano.Peer}
   	]