Added a new brush type - Random Brushes

They're like File brushes, but each time you draw, expect to see something different!

To make a random brush, just put the images you want in the same folder (under the main Brushes folder of course), and make sure their filename starts with "%".

I also changed _process() to _input() in Canvas.gd, so there may be some unexpected behavior.

Scripts/BrushButton.gd

@@ -2,6 +2,8 @@ extends BaseButton
 
 export var brush_type = Global.BRUSH_TYPES.PIXEL
 export var custom_brush_index := -2
+# warning-ignore:unused_class_variable
+var random_brushes := []
 
 func _on_BrushButton_pressed() -> void:
 	# Change left brush