[ImgBot] Optimize images

*Total -- 829.00kb -> 500.15kb (39.67%)

/solution/0400-0499/0430.Flatten a Multilevel Doubly Linked List/images/multilevellinkedlistflattened.png -- 32.72kb -> 4.87kb (85.11%)
/solution/0400-0499/0430.Flatten a Multilevel Doubly Linked List/images/multilevellinkedlist.png -- 48.47kb -> 7.81kb (83.89%)
/solution/0400-0499/0429.N-ary Tree Level Order Traversal/images/narytreeexample.png -- 30.02kb -> 8.57kb (71.44%)
/solution/0100-0199/0160.Intersection of Two Linked Lists/images/160_example_1.png -- 18.50kb -> 5.36kb (71.05%)
/solution/0100-0199/0160.Intersection of Two Linked Lists/images/160_example_2.png -- 16.26kb -> 4.74kb (70.86%)
/solution/0100-0199/0160.Intersection of Two Linked Lists/images/160_statement.png -- 19.33kb -> 5.65kb (70.78%)
/solution/0100-0199/0160.Intersection of Two Linked Lists/images/160_example_3.png -- 10.83kb -> 3.17kb (70.77%)
/solution/0200-0299/0236.Lowest Common Ancestor of a Binary Tree/images/binarytree.png -- 7.35kb -> 2.62kb (64.37%)
/solution/0200-0299/0235.Lowest Common Ancestor of a Binary Search Tree/images/binarysearchtree_improved.png -- 7.48kb -> 2.68kb (64.13%)
/solution/0100-0199/0133.Clone Graph/images/graph.png -- 1.91kb -> 0.92kb (51.69%)
/solution/0100-0199/0133.Clone Graph/images/graph-1.png -- 3.35kb -> 1.65kb (50.68%)
/solution/0200-0299/0218.The Skyline Problem/images/skyline2.png -- 16.15kb -> 8.92kb (44.75%)
/solution/0400-0499/0407.Trapping Rain Water II/images/rainwater_fill.png -- 29.44kb -> 16.31kb (44.61%)
/solution/0200-0299/0218.The Skyline Problem/images/skyline1.png -- 12.80kb -> 7.11kb (44.41%)
/solution/0400-0499/0407.Trapping Rain Water II/images/rainwater_empty.png -- 29.52kb -> 16.46kb (44.24%)
/solution/0100-0199/0138.Copy List with Random Pointer/images/e2.png -- 35.50kb -> 21.04kb (40.74%)
/solution/0100-0199/0138.Copy List with Random Pointer/images/e1.png -- 61.05kb -> 36.25kb (40.61%)
/solution/0100-0199/0116.Populating Next Right Pointers in Each Node/images/116_sample.png -- 31.80kb -> 19.10kb (39.93%)
/solution/0100-0199/0138.Copy List with Random Pointer/images/e3.png -- 47.46kb -> 28.78kb (39.37%)
/solution/0100-0199/0117.Populating Next Right Pointers in Each Node II/images/117_sample.png -- 29.89kb -> 18.42kb (38.36%)
/solution/0300-0399/0304.Range Sum Query 2D - Immutable/images/304.png -- 41.37kb -> 30.11kb (27.2%)
/solution/0000-0099/0017.Letter Combinations of a Phone Number/images/17_telephone_keypad.png -- 77.42kb -> 58.53kb (24.4%)
/lcci/16.20.T9/images/17_telephone_keypad.png -- 77.42kb -> 58.53kb (24.4%)
/solution/0000-0099/0051.N-Queens/images/8-queens.png -- 8.24kb -> 7.05kb (14.43%)
/solution/0000-0099/0052.N-Queens II/images/8-queens.png -- 8.24kb -> 7.05kb (14.43%)
/solution/0100-0199/0133.Clone Graph/images/133_clone_graph_question.png -- 70.78kb -> 64.04kb (9.52%)
/solution/0200-0299/0223.Rectangle Area/images/rectangle_area.png -- 6.02kb -> 5.49kb (8.76%)
/solution/0000-0099/0063.Unique Paths II/images/robot_maze.png -- 9.46kb -> 9.27kb (2.02%)
/solution/0000-0099/0062.Unique Paths/images/robot_maze.png -- 9.46kb -> 9.27kb (2.02%)
/solution/0400-0499/0429.N-ary Tree Level Order Traversal/images/sample_4_964.png -- 30.75kb -> 30.37kb (1.24%)

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