Add imagebox doc example for `resize` property.

lib/wibox/widget/imagebox.lua

@@ -230,6 +230,7 @@ function imagebox:set_clip_shape(clip_shape, ...)
 end
 
 --- Should the image be resized to fit into the available space?
+-- @DOC_wibox_widget_imagebox_resize_EXAMPLE@
 -- @property resize
 -- @tparam boolean resize
 

tests/examples/wibox/widget/imagebox/resize.lua

@@ -0,0 +1,46 @@
+--DOC_HIDE_ALL
+--DOC_GEN_IMAGE
+local parent    = ...
+local wibox     = require( "wibox"     )
+local beautiful = require( "beautiful" )
+
+local function cell_centered_widget(widget)
+    return wibox.widget {
+        widget,
+        valign = 'center',
+        halign = 'center',
+        content_fill_vertical = false,
+        content_fill_horizontal = false,
+        widget = wibox.container.place
+    }
+end
+
+local function build_ib(size, resize)
+    return cell_centered_widget({
+        resize = resize,
+        forced_width = size,
+        forced_height = size,
+        image  = beautiful.awesome_icon,
+        widget = wibox.widget.imagebox
+    })
+end
+
+
+local l = wibox.widget {
+    homogeneous   = false,
+    spacing       = 5,
+    layout        = wibox.layout.grid,
+}
+parent:add(l)
+
+l:add_widget_at(cell_centered_widget(wibox.widget.textbox('resize = true')), 1, 1)
+l:add_widget_at(cell_centered_widget(wibox.widget.textbox('resize = false')), 2, 1)
+l:add_widget_at(cell_centered_widget(wibox.widget.textbox('imagebox size')), 3, 1)
+
+for i,size in ipairs({16, 32, 64}) do
+    l:add_widget_at(build_ib(size, true), 1, i + 1)
+    l:add_widget_at(build_ib(size, false), 2, i + 1)
+    l:add_widget_at(cell_centered_widget(wibox.widget.textbox(size..'x'..size)), 3, i + 1)
+end
+
+--DOC_HIDE vim: filetype=lua:expandtab:shiftwidth=4:tabstop=8:softtabstop=4:textwidth=80