Allow for toggling color rendering

New menu item in Screen submenu.
hasColorScreen enabled for SDL device.

frontend/apps/reader/modules/readerrolling.lua

@@ -530,6 +530,10 @@ function ReaderRolling:onChangeScreenMode(mode)
     self:onUpdatePos()
 end
 
+function ReaderRolling:onColorRenderingUpdate()
+    self.ui.document:updateColorRendering()
+end
+
 --[[
     PosUpdate event is used to signal other widgets that pos has been changed.
 --]]