Update issue tracker to link to g suite public issue trackers (#475)

.github/ISSUE_TEMPLATE.md

@@ -3,6 +3,8 @@
 We appreciate any bug reports or other contributions, but please note that this issue
 tracker is only for this client library. We do not maintain the APIs that this client
 library talks to. If you have an issue or questions with how to use a particular API,
-you may be better off posting on Stackoverflow under the `google-api` tag.
+you may be better off posting on Stackoverflow under the `google-api` tag. If you
+are reporting an issue or requesting a feature for a G Suite API, please use their
+[public issue tracker](https://gsuite-developers.googleblog.com/2017/03/a-new-issue-tracker-for-g-suite.html)
 
 Thank you!