[ImgBot] Optimize images

*Total -- 5,851.72kb -> 5,492.82kb (6.13%)

/static/road1.png -- 220.22kb -> 130.12kb (40.92%)
/static/mountain.png -- 1,283.83kb -> 1,084.94kb (15.49%)
/static/bg.jpg -- 477.91kb -> 461.47kb (3.44%)
/static/delta.jpg -- 3,623.02kb -> 3,570.55kb (1.45%)
/css_effect/static/test.png -- 83.57kb -> 82.84kb (0.87%)
/static/moon.png -- 163.17kb -> 162.90kb (0.16%)

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

Author: ImgBotApp