- Add MouseButton enum to plugin API to determine which mouse button was pressed

- Add some missing documentation

src/DesktopMagicPluginAPI/Inputs/MouseButton.cs

@@ -0,0 +1,29 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace DesktopMagicPluginAPI.Inputs
+{
+    /// <summary>
+    /// Mouse Buttons
+    /// </summary>
+    public enum MouseButton
+    {
+        /// <summary>
+        /// The left mouse button.
+        /// </summary>
+        Left,
+
+        /// <summary>
+        /// The middle mouse button.
+        /// </summary>
+        Middle,
+
+        /// <summary>
+        ///  The right mouse button.
+        /// </summary>
+        Right,
+    }
+}