[ImgBot] Optimize images

*Total -- 630.32kb -> 549.85kb (12.77%)

/img/Screen Shot 2021-05-14 at 12.22.49 PM.png -- 242.71kb -> 189.54kb (21.91%)
/img/Screen Shot 2021-05-14 at 12.14.37 PM.png -- 76.30kb -> 64.54kb (15.42%)
/img/Screen Shot 2021-05-14 at 12.16.23 PM.png -- 142.88kb -> 134.92kb (5.57%)
/img/Screen Shot 2021-05-14 at 12.16.32 PM.png -- 168.43kb -> 160.85kb (4.5%)

Signed-off-by: ImgBotApp <[email protected]>

Author: ImgBotApp