suggestion: inform units on receiving hit

[jugglingjsons]

I was toying this idea as an alternative to handle #95 & make the actors more responsive to each other.
I was not sold on, units auto attacking in sight range, seems a bit too offensive to me, so here is the idea for a Defend Your Friend doctrine.

To be honest I am not sure if this does anything right now, I will try to test it out soon ™️

Right now it should act as a defensive reaction, where units support each other, but could also be added to the offensive stances.

If you like it, the do adjust would be the following:

• adjust the signal for offensive stance
• don't set auxiliary target on workers
• possibly filter signals by team

[Scony]

The idea looks interesting - I've been thinking about a similar thing, but simplified.
As for implementation, that's a secondary thing.
Anyway, for starters, I think it would be nice to review how well-known RTSes handle that. I'll try checking Warcraft, Starcraft, and AoE.

[berndrakell]

I also like a defensive stance more than an aggressive tbh :D Aggressive just seemed easier to implement, hence #95. In Age of Empires at least you can choose the stance of each unit (Aggressive = #95, Passive = how it was before, and defensive). Having the option to switch between different stances would be perfect obviously