add a dog-ear-like icon at the above right corner of bookmarked page

And tap the above right corner will toggle the bookmark on this page on/off.

frontend/ui/reader/readerdogear.lua

@@ -0,0 +1,16 @@
+
+ReaderDogear = RightContainer:new{}
+
+function ReaderDogear:init()
+	local widget = ImageWidget:new{
+		file = "resources/icons/dogear.png",
+	}
+	local icon_size = widget:getSize()
+	self.dimen = Geom:new{w = Screen:getWidth(), h = icon_size.h}
+	self[1] = widget
+end
+
+function ReaderDogear:onSetDogearVisibility(visible)
+	self.view.dogear_visible = visible
+	return true
+end