Add artboard name to the export when exporting a single artboard (#3613)

* add artboard name to the export

* change file name to {docname}-{artboard} for more than 1 arboard

* add switch statement instead of if else

editor/src/node_graph_executor/runtime.rs

@@ -85,6 +85,8 @@ pub struct ExportConfig {
 	pub bounds: ExportBounds,
 	pub transparent_background: bool,
 	pub size: DVec2,
+	pub artboard_name: Option<String>,
+	pub artboard_count: usize,
 }
 
 #[derive(Clone)]