Add my email in src/authors file

BUG=

Review URL: https://codereview.chromium.org/1058303004

Cr-Commit-Position: refs/heads/master@{#327467}

AUTHORS

@@ -416,6 +416,7 @@ Qi Yang <qi1988.yang@samsung.com>
 Radu Stavila <stavila@adobe.com>
 Rafael Antognolli <rafael.antognolli@intel.com>
 Raghavendra Ghatage <r.ghatage@samsung.com>
+Rahul Gupta <rahul.g@samsung.com>
 Raman Tenneti <raman.tenneti@gmail.com>
 Ramkumar Gokarnesan <ramkumar.gokarnesan@gmail.com>
 Ramkumar Ramachandra <artagnon@gmail.com>