Add a "For Object-Oriented game developers" section

Currently, the quick start guide is decent at showing what Bevy provides and how to use it, but not very good at *"how to take your prior game dev knowledge, and apply it within a new type of architecture"*. To help rectify this, we should provide a section specifically for experienced game developers that are new to ECS architecture. This section should show examples of ways to architect specific game features, like inventories, projectiles, rooms (a la Binding of Issac), enemy characters, etc.

What this section should (IMO) contain:
- Architectural comparisons between OOP and ECS (Unreal/Unity vs Bevy, generally speaking).
- Don't focus on specific nuances of any engine, so that we're resistant to API changes in any of them.
- The examples should have architectural similarity to real world games made with Bevy (used in Jam games, for example).
- Continually reinforce that the provided examples are just one way of designing within an ECS.

Obviously these examples are going to be highly vulnerable to bikeshedding, but I don't think that's necessarily a bad thing. If there's clear non-consensus on 1 way of doing something, then we should provide multiple example ways of doing that thing.

Start with the quick start guide and identify where a new section for experienced object-oriented game developers fits. Add architecture comparisons and examples covering inventories, projectiles, rooms, and enemy characters, while explaining that these are illustrative ECS designs and including alternatives where there is no consensus.

Written by the indexing model from the issue text.