[ImgBot] Optimize images

*Total -- 2,468.32kb -> 2,363.58kb (4.24%)

/docs/diagram.svg -- 7.94kb -> 6.95kb (12.45%)
/docs/harness-manager.svg -- 9.61kb -> 8.75kb (8.94%)
/docs/demo.gif -- 2,450.78kb -> 2,347.88kb (4.2%)

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

Author: ImgBotApp