[ImgBot] Optimize images

*Total -- 708.62kb -> 605.68kb (14.53%)

/.github/screnshot.png -- 153.28kb -> 116.90kb (23.74%)
/screenshot.png -- 555.34kb -> 488.79kb (11.98%)

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

Author: ImgBotApp