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/operation.rs

@@ -1,4 +1,7 @@
-use crate::{layers::style, LayerId};
+use crate::{
+	layers::{style, Layer},
+	LayerId,
+};
 
 use serde::{Deserialize, Serialize};
 
@@ -44,6 +47,10 @@ pub enum Operation {
 	DuplicateLayer {
 		path: Vec<LayerId>,
 	},
+	PasteLayer {
+		layer: Layer,
+		path: Vec<LayerId>,
+	},
 	AddFolder {
 		path: Vec<LayerId>,
 	},