[ImgBot] Optimize images

*Total -- 501.07kb -> 353.44kb (29.46%)

/readme_assets/main.png -- 184.32kb -> 127.83kb (30.65%)
/readme_assets/test.png -- 316.13kb -> 224.99kb (28.83%)
/public/vercel.svg -- 0.61kb -> 0.61kb (0.16%)

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

Author: ImgBotApp