Copy and paste layers MVP (#220)

* Initial implementation of copy and paste for layers

* Sort layers on copy and add tests

* Fix logger init for test

* Fix `copy_paste_deleted_layers` test

* Readd erroneously removed svg

* Make Layer serializable and cleanup

* Add test for copy and pasting folders

* Cleanup

* Rename left_mouseup

* Cleanup

* Add length check to test

* Fix typo

* Make mouseup, mousedown more consistent

core/document/src/layers/rect.rs

@@ -4,9 +4,10 @@ use kurbo::Point;
 use super::style;
 use super::LayerData;
 
+use serde::{Deserialize, Serialize};
 use std::fmt::Write;
 
-#[derive(Debug, Clone, PartialEq)]
+#[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
 pub struct Rect {}
 
 impl Rect {