docs: add harness example to issue template (#21078)

(cherry picked from commit 18dfd0c)

Author: annieyw

.github/ISSUE_TEMPLATE/bug.md

@@ -7,7 +7,9 @@ labels: needs triage
 
 #### Reproduction
 
-Use StackBlitz to reproduce your issue: https://stackblitz.com/fork/components-issue
+Use StackBlitz to reproduce your issue: 
+- Components: https://stackblitz.com/fork/components-issue
+- Harnesses: https://stackblitz.com/fork/harness-issue
 
 Steps to reproduce:
 1. 

.github/ISSUE_TEMPLATE/troubleshooting.md

@@ -35,7 +35,9 @@ What are you seeing that does not match your expectations?
 
 We can only help if we can reproduce the problem ourselves. 
 
-Use StackBlitz to demonstrate what you are trying to do: https://stackblitz.com/fork/components-issue 
+Use StackBlitz to demonstrate what you are trying to do: 
+- Components: https://stackblitz.com/fork/components-issue 
+- Harnesses: https://stackblitz.com/fork/harness-issue
 
 Steps to reproduce:
 1.