Add a New line button for another fingering row.

Each line keeps its own charts and staff. Save PNG stacks every line. Version 0.2.3.

Co-authored-by: catpersonisme <catpersonisme@gmail.com>

package.json

@@ -1,6 +1,6 @@
 {
   "name": "recorder-tab-converter",
-  "version": "0.2.2",
+  "version": "0.2.3",
   "private": true,
   "description": "Arrange soprano recorder fingering charts by dragging them onto a line.",
   "main": "electron/main.cjs",