Implement viewport selection (#178)

* Begin implementing viewport selection

* Implement viewport click and drag selection for ellipse and rectangle

* Begin implementing line selection

* Remove debug prints

* Run cargo format

* Use DVec2 instead of kurbo::Point

* Line and polyline intersection

* Run cargo format

* Add fix for missing layer panel update

* Replace point selection with box selection

* Formatting

Co-authored-by: Keavon Chambers <keavon@keavon.com>

core/editor/src/document/document_message_handler.rs

@@ -281,6 +281,8 @@ impl MessageHandler<DocumentMessage, &InputPreprocessor> for DocumentMessageHand
 				for path in paths {
 					responses.extend(self.select_layer(&path));
 				}
+				// TODO: Correctly update layer panel in clear_selection instead of here
+				responses.extend(self.handle_folder_changed(Vec::new()));
 			}
 			Undo => {
 				// this is a temporary fix and will be addressed by #123