Add ZeroTier check to installer

RageCoop.Core/Networking/HttpHelper.cs

@@ -0,0 +1,30 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+using System.Net;
+using System.Threading;
+
+namespace RageCoop.Core
+{
+    internal static class HttpHelper
+    {
+        public static void DownloadFile(string url,string destination,Action<int> progressCallback)
+        {
+            AutoResetEvent ae=new AutoResetEvent(false);
+            WebClient client = new WebClient();
+
+            // TLS only
+            ServicePointManager.Expect100Continue = true;
+            ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12;
+            ServicePointManager.ServerCertificateValidationCallback = delegate { return true; };
+
+            client.DownloadProgressChanged += (s, e1) => progressCallback(e1.ProgressPercentage);
+            client.DownloadFileCompleted += (s, e2) =>
+            {
+                ae.Set();
+            };
+            client.DownloadFileAsync(new Uri(url), destination);
+            ae.WaitOne();
+        }
+    }
+}