Improve code structure

- Add separate API project
- Add notification system

HyperbolicDownloaderApi/Managment/NotificationMessageEventArgs.cs

@@ -0,0 +1,21 @@
+namespace HyperbolicDownloaderApi.Managment;
+
+public class NotificationMessageEventArgs : EventArgs
+{
+    public NotificationMessageType NotificationMessageType { get; }
+    public string? Message { get; }
+
+    public NotificationMessageEventArgs(NotificationMessageType notificationMessageType, string? message)
+    {
+        NotificationMessageType = notificationMessageType;
+        Message = message;
+    }
+}
+
+public enum NotificationMessageType
+{
+    Raw,
+    Success,
+    Warning,
+    Error
+}