Add new placeable map icons on the map (e.g. biters).

[Artman40]

0.15 added a the ability to place icons on a map. Currently, you can place item and signal icons.
Some more placeable icons would be desirable.

Namely:
1. Biter, spitter and worm icons.
2. Stock alert icons (the exclamation mark one for an example).

[steinio]

Speaker signals include the stock alert icons. This could also work for map icons.
(https://mods.factorio.com/mods/Aidan647/speaker-signals)

Greetings, steinio.