[Heretic] Scripted touch action for special things
Things with the MF_SPECIAL flag can be touched for an effect like getting the health powerup.
In addition to the hardcoded functions, enable using Doomsday Script to define what happens when the special thing is touched.
Heretic|Scripting: Scripted touch action for special things
A Thing definition may specify an "On touch" script that gets run when the thing is touched. This replaces any hardcoded logic that might have affected the thing.
See the manual for an example: https://manual.dengine.net/ded/thing#on_touch