Add news post type with list and detail routes

Elternbeirat.Web/Program.cs

@@ -7,8 +7,9 @@ var builder = WebApplication.CreateBuilder(args);
 // Add services to the container.
 builder.Services.AddRazorComponents();
 
-// Content is read once at startup and cached -> singleton.
+// Content is read once at startup and cached -> singletons.
 builder.Services.AddSingleton<PageService>();
+builder.Services.AddSingleton<PostService>();
 
 var app = builder.Build();