Multi-document management (create new document; tab switching) (#210)

* Multi-docs WIP

* Change to number

* Add new document and switch documents

* Remove keybind for previous document. Change keybind for next document.

* Switch documents by clicking tabs

* Remove keybind for previous document. Change keybind for next document.

* multi-docs

* Update package-lock.json

* Hook up File>New to add new document

* Remove console logs and empty lines. Start new documents from 2 instead of 1.

* Fix formatting

core/editor/src/frontend/frontend_message_handler.rs

@@ -11,6 +11,8 @@ pub enum FrontendMessage {
 	CollapseFolder { path: Vec<LayerId> },
 	ExpandFolder { path: Vec<LayerId>, children: Vec<LayerPanelEntry> },
 	SetActiveTool { tool_name: String },
+	SetActiveDocument { document_index: usize },
+	NewDocument { document_name: String },
 	UpdateCanvas { document: String },
 	ExportDocument { document: String },
 	EnableTextInput,
@@ -38,6 +40,7 @@ impl MessageHandler<FrontendMessage, ()> for FrontendMessageHandler {
 		CollapseFolder,
 		ExpandFolder,
 		SetActiveTool,
+		NewDocument,
 		UpdateCanvas,
 		EnableTextInput,
 		DisableTextInput,