make service controller for healthchecks

Core/Controllers/Service.cs

@@ -0,0 +1,13 @@
+using Microsoft.AspNetCore.Mvc;
+
+namespace Kruzya.TelegramBot.Core.Controllers
+{
+    public class Service : ControllerBase
+    {
+        [HttpGet]
+        public ActionResult Ping()
+        {
+            return Ok("pong");
+        }
+    }
+}