Add default_config, and cfg[:timeout] for tasks

- Using the @default_config attribute in a module will fill out a default
value.
- cfg[:timeout] sets the timeout for the task for this module to finish.
- Update Omnibot.Irc.route_msg/2 to have each task spawn a second task,
  while the first task waits for its child to finish, otherwise killing
  it.

Signed-off-by: Alek Ratzloff <alekratz@gmail.com>

lib/core.ex

@@ -2,6 +2,8 @@ defmodule Omnibot.Core do
   use Omnibot.Module
   alias Omnibot.State
 
+  @default_config [channels: :all]
+
   @impl true
   def on_join(irc, channel, nick) do
     cfg = State.cfg()