[ImgBot] Optimize images

*Total -- 611.89kb -> 479.83kb (21.58%)

/css crash course/images/box-model.jpg -- 57.53kb -> 43.86kb (23.75%)
/html crash course/layout.jpg -- 63.07kb -> 48.97kb (22.36%)
/css crash course/images/inspector.jpg -- 172.48kb -> 134.25kb (22.17%)
/css crash course/images/relative-units.jpg -- 225.40kb -> 178.53kb (20.8%)
/css crash course/images/absolute-units.jpg -- 93.41kb -> 74.22kb (20.54%)

Signed-off-by: ImgBotApp <[email protected]>

Author: ImgBotApp