LinkHints: rework GetImages and change its logic
LinkHints: rework GetImages and change its logic

for `<img>`s, allow if:
* .width >= 8 || .height >= 8
* .width == .height && (.width == 3 || .width == 0)
Then judge cropped rect
* is .width is 3/0 and .width is .height, assume {width: 8, height: 8}

gdh1995/vimium-plus,gdh1995/vimium-plus,gdh1995/vimium-plus