wip: Changes of the week

- Move engine to a different crate
- Add engine trait
- Refactor the rest of the codebase to work with these changes
- Add debug ui buffer, use it to finish imgui support

core/src/context.rs

@@ -1,16 +1,11 @@
 use std::cell::RefCell;
 use std::rc::Rc;
+use std::sync::Arc;
 use winit::event::Event;
 use raidillon_assets::{ModelManagerRef, ModelManager};
 
-// TODO: Find a way to move this to raidillon_platform as it belongs there.
-// TODO: The name "Context" doesn't imply the wide role of this structure.
-
-/// This provides a bridge between the game logic systems (raidillon_core::System) and
-/// platform-related data/utilities.
 #[derive(Clone)]
 pub struct PlatformContext {
-    /// The latest winit event.
     pub current_event: Event<()>,
     pub asset_manager: ModelManagerRef,
     pub frame_width: f32,