[ImgBot] Optimize images

*Total -- 1,248.55kb -> 1,095.72kb (12.24%)

/.github/screnshot.png -- 693.21kb -> 606.94kb (12.45%)
/screenshot.png -- 555.34kb -> 488.79kb (11.98%)

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

Author: ImgBotApp