doc: change mentions of "ECS architecture" to a more proper description

[LuanHimmlisch]

Currently Kaplay, mentions a list of features both on the PressKit and itch page.

But the claim of ECS, as of v3001, is incorrect.

An ECS (Entity Component System) architecture.

Entity-Component-System Architecture is a very specific way to decouple data and logic, to obtain better performance. This Kaplay doesn't do.

Seeing the development of v4000 in #565, it seems there are efforts to try to adhere to the architecture.
But at the time, it seems purely as an internal event bus and, as I understand it, the users will be able to create their own systems as an opt-in functionality, the entities are not decoupled by default.

I propose changing the mentions of ECS to a better fitting name, such as:

• Composition Over Inheritance Architecture.
• Entity-Component Architecture.

The 1st being the more proper formal way. The 2nd, is more of a informal way to refer to this kind of decoupling of behavior and game-objects that aren't fully ECS.

If the System in ECS is added, maybe a more explicit extra feature could be added such as:

• Optional ECS functionality.

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Researching about this today, I found previous discussions on the Discord about this topic. Finding some people confused saying that "Kaplay is easier to use than other ECS engines", while yes it's true Kaplay is easier to use, it is so because it's not an actual ECS. It's important to have the proper terminology specially for novices that may get the wrong ideas.

[lajbel]

Systems were already added. we will keep the definition because it is broadly an ESC. I will also consider other architectures anyway