[ImgBot] Optimize images

*Total -- 300.48kb -> 257.44kb (14.32%)

/public/assets/imgs/blog/giscus.jpg -- 45.46kb -> 34.17kb (24.84%)
/public/assets/imgs/blog/utterances.jpg -- 79.39kb -> 61.41kb (22.65%)
/diagram.svg -- 175.64kb -> 161.87kb (7.84%)

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

Author: ImgBotApp