Update README - Topic Tags

Author: Sangram03

README.md

@@ -58,6 +58,7 @@ I want share my updates on daily basis practice.
 | [3309-count-prefix-and-suffix-pairs-i](https://github.com/Sangram03/Leetcode/tree/master/3309-count-prefix-and-suffix-pairs-i) |
 | [3427-special-array-ii](https://github.com/Sangram03/Leetcode/tree/master/3427-special-array-ii) |
 | [3555-final-array-state-after-k-multiplication-operations-i](https://github.com/Sangram03/Leetcode/tree/master/3555-final-array-state-after-k-multiplication-operations-i) |
+| [3685-count-subarrays-of-length-three-with-a-condition](https://github.com/Sangram03/Leetcode/tree/master/3685-count-subarrays-of-length-three-with-a-condition) |
 ## Hash Table
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