update 'social' in _config.yml

Signed-off-by: Leonid Belenkiy <[email protected]>

_config.yml

@@ -42,7 +42,7 @@ social:
   links:
     # The first element serves as the copyright owner's link
     # - https://twitter.com/username # change to your twitter homepage
-    # - https://github.com/username # change to your github homepage
+    - https://github.com/username # change to your github homepage
     # Uncomment below to add more social links
     # - https://www.facebook.com/username
     # - https://www.linkedin.com/in/username