Add command line interface and change solution structure (#26)

DiscordChatExporter.Gui/Program.cs

@@ -0,0 +1,17 @@
+using System;
+using AmmySidekick;
+
+namespace DiscordChatExporter.Gui
+{
+    public static class Program
+    {
+        [STAThread]
+        public static void Main()
+        {
+            var app = new App();
+            app.InitializeComponent();
+            RuntimeUpdateHandler.Register(app, $"/{Ammy.GetAssemblyName(app)};component/App.g.xaml");
+            app.Run();
+        }
+    }
+}