saving and displaying the configured library dir

frontend/wailsjs/go/main/App.d.ts

@@ -2,3 +2,5 @@
 // This file is automatically generated. DO NOT EDIT
 
 export function DirectoryPicker():Promise<string>;
+
+export function GetLibraryDir():Promise<string>;

frontend/wailsjs/go/main/App.js

@@ -5,3 +5,7 @@
 export function DirectoryPicker() {
   return window['go']['main']['App']['DirectoryPicker']();
 }
+
+export function GetLibraryDir() {
+  return window['go']['main']['App']['GetLibraryDir']();
+}