Make MainWindow public so that Plugins can access it.

ILSpy/MainWindow.xaml

@@ -1,7 +1,7 @@
 <?xml version="1.0" encoding="utf-8"?>
 <Window
 	x:Class="ICSharpCode.ILSpy.MainWindow"
-	x:ClassModifier="internal"
+	x:ClassModifier="public"
 	xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:tv="clr-namespace:ICSharpCode.TreeView;assembly=ICSharpCode.TreeView"
 	xmlns:local="clr-namespace:ICSharpCode.ILSpy" xmlns:textView="clr-namespace:ICSharpCode.ILSpy.TextView"
 	xmlns:controls="clr-namespace:ICSharpCode.ILSpy.Controls"