Update README with LeetCode Daily Challenge

Author: jeremymanning

README.md

@@ -15,6 +15,7 @@ Each day (ideally) we'll attempt the daily [leetcode](https://leetcode.com) prob
 | July 4, 2024 | [2181](https://leetcode.com/problems/merge-nodes-in-between-zeros/)                                         | [Click here](https://github.com/ContextLab/leetcode-solutions/tree/main/problems/2181)                    | 🟡  Medium      |
 | July 5, 2024 | [2058](https://leetcode.com/problems/find-the-minimum-and-maximum-number-of-nodes-between-critical-points/) | [Click here](https://github.com/ContextLab/leetcode-solutions/tree/main/problems/2058)                    | 🟡  Medium      |
 | July 6, 2024 | [2582](https://leetcode.com/problems/pass-the-pillow) | [Click here](https://github.com/ContextLab/leetcode-solutions/tree/main/problems/2582) | 🟢 Easy |
+| July 7, 2024 | [1518](https://leetcode.com/problems/water-bottles) | [Click here](https://github.com/ContextLab/leetcode-solutions/tree/main/problems/1518) | 🟢 Easy |
 
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