Added a selection for BrushCalculationModes (relative/absolute)

Devices/Keyboard/Enums/BrushCalculationMode.cs

@@ -0,0 +1,17 @@
+namespace CUE.NET.Devices.Keyboard.Enums
+{
+    /// <summary>
+    /// Contains list of all brush calculation modes.
+    /// </summary>
+    public enum BrushCalculationMode
+    {
+        /// <summary>
+        /// The calculation rectangle for brushes will be the rectangle around the keygroup the brush is applied to.
+        /// </summary>
+        Relative,
+        /// <summary>
+        /// The calculation rectangle for brushes will always be the whole keyboard.
+        /// </summary>
+        Absolute
+    }
+}