[ImgBot] Optimize images

*Total -- 7,961.24kb -> 7,617.27kb (4.32%)

/absolute-beginners/full-stack/internet-basics/02.png -- 1,637.40kb -> 1,538.03kb (6.07%)
/absolute-beginners/full-stack/internet-basics/03.png -- 1,961.30kb -> 1,867.17kb (4.8%)
/absolute-beginners/full-stack/internet-basics/04.png -- 2,156.50kb -> 2,074.71kb (3.79%)
/static/img/tutorials/how-browsers-work.png -- 2,206.05kb -> 2,137.36kb (3.11%)

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

Author: ImgBotApp