Small breaking change

[Dirkster99]

I saw through code search here on GitHUb that you are using Dirkster.AvalonDock.Themes.VS2013

This is just a small note to let you know that we will have a small breaking change in the next nugget version 3.5.9 in naming of one ResourceKey:

• DockingButtonForegroundArrowBrusKey -> DockingButtonForegroundArrowBrushKey

as documented here: #52.

I see that you use AvalonEdit with theming so AvalonEditHighlightingThemes might be interesting for you.