Add TypeScript solution for duplicate finder

Added TypeScript implementation for finding duplicates.

Author: yanglbme

solution/0400-0499/0442.Find All Duplicates in an Array/README.md

@@ -146,6 +146,27 @@ func findDuplicates(nums []int) []int {
 }
 ```
 
+#### TypeScript
+
+```ts
+function findDuplicates(nums: number[]): number[] {
+    for (let i = 0; i < nums.length; i++) {
+        while (nums[i] !== nums[nums[i] - 1]) {
+            const temp = nums[i];
+            nums[i] = nums[temp - 1];
+            nums[temp - 1] = temp;
+        }
+    }
+    const ans: number[] = [];
+    for (let i = 0; i < nums.length; i++) {
+        if (nums[i] !== i + 1) {
+            ans.push(nums[i]);
+        }
+    }
+    return ans;
+}
+```
+
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