[ImgBot] Optimize images

*Total -- 15,007.34kb -> 14,108.42kb (5.99%)

/assets/cars.gif -- 8,105.16kb -> 7,490.41kb (7.58%)
/assets/cows.gif -- 6,902.18kb -> 6,618.01kb (4.12%)

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

Author: ImgBotApp