Update Readme.md

Author: wisdompeak

Readme.md

@@ -997,6 +997,7 @@
 [1401.Circle-and-Rectangle-Overlapping](https://github.com/wisdompeak/LeetCode/tree/master/Math/1401.Circle-and-Rectangle-Overlapping) (H) 
 [1453.Maximum-Number-of-Darts-Inside-of-a-Circular-Dartboard](https://github.com/wisdompeak/LeetCode/tree/master/Math/1453.Maximum-Number-of-Darts-Inside-of-a-Circular-Dartboard) (H) 
 [1610.Maximum-Number-of-Visible-Points](https://github.com/wisdompeak/LeetCode/tree/master/Math/1610.Maximum-Number-of-Visible-Points) (H) 
+[2280.Minimum-Lines-to-Represent-a-Line-Chart](https://github.com/wisdompeak/LeetCode/tree/master/Math/2280.Minimum-Lines-to-Represent-a-Line-Chart) (M) 
 * ``Random Pick`` 
 [382.Linked-List-Random-Node](https://github.com/wisdompeak/LeetCode/tree/master/Math/382.Linked-List-Random-Node) (H) 
 [470.Implement-Rand10()-Using-Rand7()](https://github.com/wisdompeak/LeetCode/tree/master/Math/470.Implement-Rand10--Using-Rand7) (M+)