Update README with LeetCode Daily Challenge

Author: jeremymanning

README.md

@@ -206,6 +206,7 @@ _**Note:** Our group is currently taking a break from grinding leetcode. The tab
 | January 9, 2025 | [2185](https://leetcode.com/problems/counting-words-with-a-given-prefix/description/?envType=daily-question) | [Click here](https://github.com/ContextLab/leetcode-solutions/tree/main/problems/2185) | 🟢 Easy |
 | January 10, 2025 | [916](https://leetcode.com/problems/word-subsets/description/?envType=daily-question) | [Click here](https://github.com/ContextLab/leetcode-solutions/tree/main/problems/916) | 🟡 Medium |
 | January 11, 2025 | [1400](https://leetcode.com/problems/construct-k-palindrome-strings/description/?envType=daily-question) | [Click here](https://github.com/ContextLab/leetcode-solutions/tree/main/problems/1400) | 🟡 Medium |
+| January 12, 2025 | [2116](https://leetcode.com/problems/check-if-a-parentheses-string-can-be-valid/description/?envType=daily-question) | [Click here](https://github.com/ContextLab/leetcode-solutions/tree/main/problems/2116) | 🟡 Medium |
 
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