[ImgBot] Optimize images

*Total -- 97.25kb -> 61.80kb (36.46%)

/assets/screenshot/yourscreenshot.png -- 65.56kb -> 37.47kb (42.85%)
/assets/appstore.png -- 12.69kb -> 7.44kb (41.37%)
/assets/playstore.png -- 16.75kb -> 14.73kb (12.07%)
/assets/squircle120.svg -- 1.10kb -> 1.05kb (4.18%)
/assets/squircle.svg -- 1.16kb -> 1.11kb (3.97%)

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

Author: ImgBotApp