Implement menu bar floating list menus (#163)

Progress towards #135

client/web/wasm/src/document.rs

@@ -92,6 +92,12 @@ pub fn reset_colors() -> Result<(), JsValue> {
 	EDITOR_STATE.with(|editor| editor.borrow_mut().handle_message(ToolMessage::ResetColors)).map_err(convert_error)
 }
 
+/// Undo history one step
+#[wasm_bindgen]
+pub fn undo() -> Result<(), JsValue> {
+	EDITOR_STATE.with(|editor| editor.borrow_mut().handle_message(DocumentMessage::Undo)).map_err(convert_error)
+}
+
 /// Select a layer from the layer list
 #[wasm_bindgen]
 pub fn select_layer(path: Vec<LayerId>) -> Result<(), JsValue> {