Update README with LeetCode Daily Challenge

Author: jeremymanning

README.md

@@ -199,6 +199,7 @@ _**Note:** Our group is currently taking a break from grinding leetcode. The tab
 | January 2, 2025 | [2559](https://leetcode.com/problems/count-vowel-strings-in-ranges/description/?envType=daily-question) | [Click here](https://github.com/ContextLab/leetcode-solutions/tree/main/problems/2559) | 🟡 Medium |
 | January 3, 2025 | [2270](https://leetcode.com/problems/number-of-ways-to-split-array/description/?envType=daily-question) | [Click here](https://github.com/ContextLab/leetcode-solutions/tree/main/problems/2270) | 🟡 Medium |
 | January 4, 2025 | [1930](https://leetcode.com/problems/unique-length-3-palindromic-subsequences/description/?envType=daily-question) | [Click here](https://github.com/ContextLab/leetcode-solutions/tree/main/problems/1930) | 🟡 Medium |
+| January 5, 2025 | [2381](https://leetcode.com/problems/shifting-letters-ii/description/?envType=daily-question) | [Click here](https://github.com/ContextLab/leetcode-solutions/tree/main/problems/2381) | 🟡 Medium |
 
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