[ImgBot] Optimize images

*Total -- 139.84kb -> 117.62kb (15.9%)

/assets/Sun.png -- 13.21kb -> 7.40kb (43.97%)
/assets/Moon.png -- 126.64kb -> 110.21kb (12.97%)

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

Author: ImgBotApp