[ImgBot] Optimize images

*Total -- 1,238.62kb -> 1,087.63kb (12.19%)

/.github/screnshot.png -- 683.28kb -> 598.84kb (12.36%)
/screenshot.png -- 555.34kb -> 488.79kb (11.98%)

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

Author: ImgBotApp