feat: added additional selected menu item indicator

closes #853

src/uosc/elements/Menu.lua

@@ -1221,6 +1221,15 @@ function Menu:render()
 					opacity = highlight_opacity * menu_opacity,
 					clip = item_clip,
 				})
+
+				-- Selected item indicator line
+				if is_selected then
+					local size = round(2 * state.scale)
+					local v_padding = math.min(state.radius, math.ceil(self.item_height / 3))
+					ass:rect(ax + self.padding - size - 1, item_ay + v_padding, ax + self.padding - 1, item_by - v_padding, {
+						radius = 1, color = fg, opacity = menu_opacity, clip = item_clip,
+					})
+				end
 			end
 
 			-- Icon