[ImgBot] Optimize images

*Total -- 357.89kb -> 263.36kb (26.41%)

/assets/img/screenshots/Screenshot.png -- 192.86kb -> 130.18kb (32.5%)
/assets/img/screenshots/Screenshot_minimal.png -- 59.66kb -> 47.45kb (20.46%)
/assets/img/screenshots/Screenshot_code_highlight.png -- 44.59kb -> 35.61kb (20.13%)
/assets/img/screenshots/Screenshot_mobile.png -- 39.27kb -> 31.46kb (19.9%)
/assets/img/logo.jpg -- 21.51kb -> 18.66kb (13.29%)

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

Author: ImgBotApp