Fix: Add UseStaticFiles() to serve RCL static assets

MapStaticAssets() alone doesn't serve _content files from Razor Class Libraries.
Adding UseStaticFiles() ensures autocomplete CSS files are properly served.

Fixes 404 errors for:
- _content/EasyAppDev.Blazor.AutoComplete/styles/autocomplete.base.css
- _content/EasyAppDev.Blazor.AutoComplete/styles/autocomplete.themes.css

Author: mashrulhaque

samples/AutoComplete.Playground/Program.cs

@@ -41,6 +41,7 @@
 
 app.UseAntiforgery();
 
+app.UseStaticFiles();
 app.MapStaticAssets();
 app.MapRazorComponents<App>()
     .AddInteractiveServerRenderMode();