[ImgBot] Optimize images

*Total -- 160.33kb -> 144.12kb (10.11%)

/imgs/plugin_menu.png -- 8.06kb -> 6.40kb (20.56%)
/imgs/plugin_page.png -- 107.38kb -> 96.71kb (9.94%)
/imgs/plugin_posts.png -- 31.99kb -> 29.13kb (8.92%)
/imgs/plugin_activation.png -- 12.65kb -> 11.63kb (8.07%)
/src/player/errormark.svg -- 0.26kb -> 0.25kb (3%)

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

Author: ImgBotApp