docs(issue): update issue template

.github/ISSUE_TEMPLATE/bug_report.md

@@ -1,24 +1,41 @@
 ---
 name: Bug report
-about: If rxjs does not behave as expected
+about: Reporting bugs for rxjs core behavior
 
 ---
 
+<!--
+
+PLEASE READ BEFORE FILING AN ISSUE
+
+Rxjs uses github issues (https://github.com/ReactiveX/rxjs/issues) as core team's issue backlog only.
+For community contributions please use discussions (https://github.com/ReactiveX/rxjs/discussions) instead.
+
+If you believe there is a bug in rxjs core need to be fixed, please fill out all template for repro, otherwise
+core team may move issues into discussions. Also, all other non-bug report may closed without followup.
+
+Thanks!
+ -->
+
 ## Bug Report
 
 **Current Behavior**
 A clear and concise description of the behavior.
 
+**Expected behavior**
+A clear and concise description of what you expected to happen (or code).
+
 **Reproduction**
+
+** Please provide repro code does not involves framework, or other setups to address this bug is specific to rxjs core **
+
 - REPL or Repo link:
 (you can use https://stackblitz.com/ to create one to attach here)
 
 ```js
 var your => (code) => here;
 ```
 
-**Expected behavior**
-A clear and concise description of what you expected to happen (or code).
 
 **Environment**
 - Runtime: [e.g. Node v${x}, Chrome v${x}]