Update README_EN.md

Just added the rust implementation of this problem .  It is tested on the leetcode and it successfully passed all test .

Author: shitcodebykaushik

solution/1900-1999/1929.Concatenation of Array/README_EN.md

@@ -158,7 +158,18 @@ int* getConcatenation(int* nums, int numsSize, int* returnSize) {
     return ans;
 }
 ```
-
+### Rust 
+```Rust
+impl Solution {
+    pub fn get_concatenation(mut nums: Vec<i32>) -> Vec<i32> {
+        let original_len = nums.len();
+        for i in 0..original_len {
+            nums.push(nums[i]);
+        }
+        nums
+    }
+}
+```
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 <!-- solution:end -->