Add Fake DNS support (#309)

Co-authored-by: Xiaokang Wang <xiaokangwang@outlook.com>
Co-authored-by: loyalsoldier <10487845+Loyalsoldier@users.noreply.github.com>
Co-authored-by: kslr <kslrwang@gmail.com>

app/dns/fakedns/fakedns.proto

@@ -0,0 +1,12 @@
+syntax = "proto3";
+
+package xray.app.dns.fakedns;
+option csharp_namespace = "Xray.App.Dns.Fakedns";
+option go_package = "github.com/xtls/xray-core/app/dns/fakedns";
+option java_package = "com.xray.app.dns.fakedns";
+option java_multiple_files = true;
+
+message FakeDnsPool{
+  string ip_pool = 1; //CIDR of IP pool used as fake DNS IP
+  int64  lruSize = 2; //Size of Pool for remembering relationship between domain name and IP address
+}