[ImgBot] Optimize images

*Total -- 132.54kb -> 78.40kb (40.85%)

/screenshot/preview.png -- 32.85kb -> 19.16kb (41.69%)
/screenshot/settings.png -- 75.10kb -> 44.36kb (40.93%)
/screenshot/main.png -- 23.87kb -> 14.31kb (40.04%)
/resources/META-INF/pluginIcon.svg -- 0.72kb -> 0.57kb (20.9%)

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

Author: ImgBotApp