[ImgBot] Optimize images

*Total -- 99.77kb -> 66.30kb (33.55%)

/part0/0.5.png -- 33.77kb -> 13.70kb (59.43%)
/part0/0.6.png -- 15.34kb -> 6.40kb (58.28%)
/part0/0.4.png -- 50.66kb -> 46.20kb (8.82%)

Signed-off-by: ImgBotApp <ImgBotHelp@gmail.com>

Author: ImgBotApp