[ImgBot] Optimize images

*Total -- 630.85kb -> 593.29kb (5.95%)

/context-menu.png -- 46.10kb -> 39.19kb (14.99%)
/screenshot.png -- 333.34kb -> 309.99kb (7.01%)
/dracula_withborder.png -- 126.73kb -> 123.03kb (2.93%)
/dracula_withoutborder.png -- 124.67kb -> 121.08kb (2.88%)

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

Author: ImgBotApp