Adding prettier error handling page in the pipeline

BTCPayServer/Controllers/ErrorController.cs

@@ -0,0 +1,18 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using Microsoft.AspNetCore.Mvc;
+
+namespace BTCPayServer.Controllers
+{
+    [Route("[controller]/[action]")]
+    public class ErrorController : Controller
+    {
+        public IActionResult Handle(int? statusCode = null)
+        {
+            return View(statusCode);
+        }
+    }
+}