Update ISSUE_TEMPLATE

Author: natemcmaster

.github/ISSUE_TEMPLATE

@@ -1,3 +1,6 @@
+If you are having an issue with microsoft/aspnet, please open an issue on https://github.com/Microsoft/aspnet-docker.
+This repository is for microsoft/aspnetcore and microsoft/aspnetcore-build.
+
 ## Steps to reproduce the issue
 (e.g. copy your Dockerfile or docker-compose.yml file here)
 1.