feat: replace with absolute url

Author: lucifer

collections/easy.md

@@ -1,6 +1,6 @@
 - [面试题 17.12. BiNode](../problems/binode-lcci.md) 🆕
 
-- [0001.two-sum](../problems/1.two-sum.md)
+- [0001.two-sum](https://github.com/azl397985856/leetcode/blob/master/problems/1.two-sum.md)
 - [0020.Valid Parentheses](../problems/20.valid-parentheses.md)
 - [0021.MergeTwoSortedLists](../problems/21.merge-two-sorted-lists.md)
 - [0026.remove-duplicates-from-sorted-array](../problems/26.remove-duplicates-from-sorted-array.md)