Draft Box primitive

wgpu/src/renderer.rs

@@ -144,6 +144,9 @@ impl Renderer {
                 scale: wgpu_glyph::Scale { x: *size, y: *size },
                 ..Default::default()
             }),
+            Primitive::Box { bounds, background } => {
+                // TODO: Batch boxes and draw them all at once
+            }
         }
     }
 }