add module system and move sensor into core with it

src/layout/layer.rs

@@ -1,9 +1,9 @@
 use std::ops::{Index, IndexMut};
 
 use crate::{
-    layout::{SenseShape, UiRegion},
+    layout::UiRegion,
     render::{Primitive, PrimitiveHandle, Primitives},
-    util::{HashMap, Id},
+    util::Id,
 };
 
 struct LayerNode {
@@ -26,10 +26,10 @@ pub struct Layers {
     vec: Vec<LayerNode>,
 }
 
+/// TODO: this can be replaced with Primitives itself atm
 #[derive(Default)]
 pub struct Layer {
     pub primitives: Primitives,
-    pub sensors: HashMap<Id, SenseShape>,
 }
 
 impl Layers {