chore(docs): add test app link to issue template (#3843)

Author: juliemr

.github/ISSUE_TEMPLATE

@@ -6,7 +6,7 @@ To help us help you better, please do the following before submitting an issue:
 
 1. Review the questions section of [CONTRIBUTING.md](https://github.com/angular/protractor/blob/master/CONTRIBUTING.md#contributing).
 2. Make sure you are not asking a usage or debugging question. If you are, use [StackOverflow](http://stackoverflow.com/questions/tagged/protractor), [Google Group discussion list](https://groups.google.com/forum/?fromgroups#!forum/angular), or [Gitter](https://gitter.im/angular/protractor) to get help.
-3. Provide a minimally reduced test case. This makes it much more likely that your bug will be fixed.
+3. Provide a minimally reduced test case. This makes it much more likely that your bug will be fixed. Protractor has a test Angular application available at `http://www.protractortest.org/testapp` which you can use for the reproducible test case.
 4. Fill in the information that corresponds to your type of issue below.
 5. Delete this intro and any unrelated text :smile: (if you do not we'll assume you haven't read these instructions and automatically close the issue.)