[ImgBot] Optimize images

*Total -- 161.14kb -> 53.31kb (66.92%)

/images/step1.png -- 27.95kb -> 7.53kb (73.06%)
/images/mru.png -- 38.12kb -> 10.42kb (72.68%)
/images/fzf.png -- 29.02kb -> 8.47kb (70.81%)
/images/complete-2.png -- 28.69kb -> 9.05kb (68.46%)
/images/complete-1.png -- 12.35kb -> 5.12kb (58.53%)
/images/step2.png -- 12.63kb -> 5.66kb (55.16%)
/images/step3.png -- 7.56kb -> 3.63kb (52.03%)
/images/step4.png -- 4.83kb -> 3.44kb (28.77%)

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

Author: ImgBotApp