[ImgBot] Optimize images

*Total -- 3,700.00kb -> 2,950.06kb (20.27%)

/image/ss6.png -- 87.94kb -> 33.37kb (62.05%)
/image/ss5.png -- 99.93kb -> 40.85kb (59.12%)
/image/ss4.png -- 89.29kb -> 37.92kb (57.53%)
/image/ss7.png -- 110.04kb -> 48.84kb (55.62%)
/image/flute3.png -- 219.77kb -> 162.94kb (25.86%)
/image/fe.png -- 219.35kb -> 167.38kb (23.69%)
/image/ss3.png -- 68.30kb -> 52.65kb (22.92%)
/image/fa.png -- 403.74kb -> 319.66kb (20.83%)
/image/ss1.png -- 209.04kb -> 177.62kb (15.03%)
/image/ss2.png -- 2,192.58kb -> 1,908.84kb (12.94%)

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

Author: ImgBotApp