[ImgBot] Optimize images

*Total -- 1,225.99kb -> 1,083.40kb (11.63%)

/screenshot.png -- 555.34kb -> 488.79kb (11.98%)
/.github/screnshot.png -- 670.65kb -> 594.61kb (11.34%)

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

Author: ImgBotApp