[ImgBot] Optimize images

*Total -- 1,526.60kb -> 460.16kb (69.86%)

/img/leetcode-github-yanglbme.png -- 1,031.76kb -> 69.14kb (93.3%)
/img/random-list-step3.png -- 6.00kb -> 2.47kb (58.85%)
/img/random-list-step2.png -- 6.00kb -> 2.74kb (54.3%)
/img/random-list-step1.png -- 5.00kb -> 2.30kb (54.02%)
/img/how-to-contribute-yanglbme.png -- 17.66kb -> 8.87kb (49.8%)
/img/random-list.png -- 3.00kb -> 1.64kb (45.38%)
/img/Largest-Component-Size-by-Common-Factor3.png -- 108.87kb -> 80.97kb (25.63%)
/img/create-pull-request.png -- 59.45kb -> 47.54kb (20.03%)
/img/dev-pull-request.png -- 58.74kb -> 47.94kb (18.38%)
/img/brick_wall.png -- 44.48kb -> 36.52kb (17.9%)
/img/Largest-Component-Size-by-Common-Factor2.png -- 14.42kb -> 11.91kb (17.4%)
/img/email-of-pull-request.jpg -- 81.51kb -> 67.49kb (17.21%)
/img/clone-fork-doocs-leetcode.jpg -- 67.80kb -> 59.47kb (12.28%)
/img/Largest-Component-Size-by-Common-Factor1.png -- 12.45kb -> 11.90kb (4.48%)
/img/robot_maze.png -- 9.46kb -> 9.27kb (2.02%)

Author: ImgBotApp