Add readme.md for benchmark

Benchmark/README.md

+# Benchmark Result
+***
+
+### Generated kid data benchmark with MXnet ArcFace origin
+***
+
+- 200 sampling image test IP distance:
+![alt](./Gen_kid/result_kid_gen_IP.png)
+
+- 200 sampling image test L2 distance:
+![alt](./Gen_kid/result_kid_gen_L2.png)
+
+### Real kid data benchmark with MXnet ArcFace origin
+***
+- 265 sampling image test IP distance:
+![alt](./Real_kid/result_kid_real_IP.png)
+
+- 265 sampling image test L2 distance:
+![alt](./Real_kid/result_kid_real_L2.png)
+
+### Real adult data benchmark with MXnet ArcFace origin
+***
+
+- 200 sampling image test IP distance:
+![alt](./adult_real/result_adult_real_IP.png)
+
+- 200 sampling image test L2 distance:
+![alt](./adult_real/result_adult_real_L2.png)
+
+## Note
+- L2 distance: smaller score, better result
+- IP distance: higher score, better result
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