Added several CallGS handlers.

GameServer/Server/CallGS/Handlers/Misc/LanguageChange.cs

@@ -0,0 +1,10 @@
+namespace MikuSB.GameServer.Server.CallGS.Handlers.Misc;
+
+// Client notifies the server of its language setting. No response required.
+// param: {nType, sLan, sEx}
+[CallGSApi("LanguageChange")]
+public class LanguageChange : ICallGSHandler
+{
+    public Task Handle(Connection connection, string param, ushort seqNo)
+        => Task.CompletedTask;
+}

GameServer/Server/CallGS/Handlers/Misc/ZoneTime_ReqTime.cs

@@ -0,0 +1,16 @@
+using MikuSB.Util.Extensions;
+
+namespace MikuSB.GameServer.Server.CallGS.Handlers.Misc;
+
+// Client requests server time to calculate timezone offset.
+// nTime1/nTime2 are DST transition reference timestamps; returning the same value means no offset.
+[CallGSApi("ZoneTime_ReqTime")]
+public class ZoneTime_ReqTime : ICallGSHandler
+{
+    public async Task Handle(Connection connection, string param, ushort seqNo)
+    {
+        var now = Extensions.GetUnixSec();
+        var arg = $"{{\"nTime1\":{now},\"nTime2\":{now}}}";
+        await CallGSRouter.SendScript(connection, "ZoneTime_ChangeTime", arg, seqNo);
+    }
+}