[ImgBot] Optimize images

*Total -- 1,272.68kb -> 1,118.29kb (12.13%)

/.github/screnshot.png -- 717.34kb -> 629.51kb (12.24%)
/screenshot.png -- 555.34kb -> 488.79kb (11.98%)

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

Author: ImgBotApp