Run GetShowsAsync in the background

This allows for faster startup because initializing and checking the cache doesn't block the UI thread.

src/Mobile/ViewModels/DiscoverViewModel.cs

@@ -49,7 +49,9 @@ public class DiscoverViewModel : BaseViewModel
 
     private async Task FetchAsync()
     {
-        var podcastsModels = await showsService.GetShowsAsync();
+        // run GetShowsAsync in the background, so things get initialized in the background
+        // like checking the cache and the web request
+        var podcastsModels = await Task.Run(() => showsService.GetShowsAsync());
 
         if (podcastsModels == null)
         {