1. restore background color
2. fix border radius on top/bottom and on hover
3. parent link is now full-row again, much easier to click
4. parent link now uses directory icon, matching github
5 changed grid layout to remove auto width on file name column which could get too small.
6. mobile layout now shows more of the filename.
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Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>