[ImgBot] Optimize images

*Total -- 2,682.57kb -> 1,678.32kb (37.44%)

/example-preview.png -- 2,664.85kb -> 1,665.20kb (37.51%)
/assets/lambdalogo.png -- 17.71kb -> 13.12kb (25.9%)

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

Author: ImgBotApp