[ImgBot] Optimize images

*Total -- 4,320.32kb -> 4,043.20kb (6.41%)

/public/media/authors/gading-chibi-close.png -- 1,390.28kb -> 1,296.74kb (6.73%)
/public/media/authors/gading-chibi-close-signature.png -- 1,390.28kb -> 1,296.74kb (6.73%)
/public/media/authors/gading-chibi-talk-signature.png -- 1,539.76kb -> 1,449.72kb (5.85%)

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

Author: ImgBotApp