feat: add MSU.Class.Event class

[LordMidas]

This emulates event listeners. Now someone can raise an event without having to know who is listening to the event.

[TaroEld]

Feels to me like this should perhaps be based on the actual functions that are being called,ie if they return false then stop or something along those lines.

[LordMidas]

Nah, those functions can be anything. They don't necessarily have to be Boolean returning functions. This conditionalInvoke is more along the lines of replicating the isAlive feature of skill_container events where the iteration stops if the actor is no longer alive.

[TaroEld]

Returning false to stop an event from continuing feels quite natural, it's how it's done in JS event bubbling for example. Using some otherwise decoupled thing to check for a state is weird in contrast.

[TaroEld]

Do we have an usecase for this?

[LordMidas]

Do we have an usecase for this?

I mean event listeners are a basic thing in programming and I'm sure people will find use cases for this. It will help modders write more decoupled code.

[TaroEld]

I'm wondering if keeping the env around like that doesn't lead to a risk of memory leaks.

[TaroEld]

Also, if this shouldn't keep a dict of events, with arrays for each of course.
Then, we might even consider filling them up with default events/stacks.
One for world_state, one for tactical_state, for example.