[ImgBot] Optimize images

*Total -- 138.87kb -> 123.16kb (11.31%)

/assets/icons/soleliten.png -- 20.63kb -> 16.13kb (21.83%)
/assets/icons/amundsen.jpg -- 69.33kb -> 58.81kb (15.18%)
/assets/icons/plussagenturer.jpg -- 23.59kb -> 23.09kb (2.1%)
/assets/icons/wj.jpg -- 10.29kb -> 10.13kb (1.52%)
/assets/icons/sprell.jpg -- 15.03kb -> 15.00kb (0.17%)

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

Author: ImgBotApp