custom_type and event for alert

[meifray]

Alert now have member: custom_type::string

• The custom type of alert,or nil if it is not specify

add_custom_alert now take optional field: custom_type::string

• when not specify,default to nil.

Custom Alert with differnt custom_type will be sort into different group in gui.


new event:defines.events.on_player_clicked_alert

• Called when a player clicked a alert group.
• Fields:
  • player_index
    :: uint
    The player who clicked a alert.
  • alerts
    :: array[Alert]
    The Alert group player clicked
  • name
    :: defines.events
    Identifier of the event
  • tick
    :: uint