Api function to reload all tym instances about tym

[endaaman]

A combination of get_ids API and signals might help.

tym.set_keymap('<Ctrl>0', function()
  for id in pairs(tym.get_ids()) do
    tym.signal(id, 'hook', {'reload'})
  end
end)

tym.set_hook('signal', function(command)
  if command == 'reload' then
    tym.reload()
    return
  end
end)

Also added some docs to README about these IPC stuffs ( 5574e86 ), thanks.