Update the bug report template with comments

.github/ISSUE_TEMPLATE/bug_report.md

@@ -8,29 +8,30 @@ assignees: guzongmin
 ---
 
 <!--- Provide a general summary of the issue in the Title above -->
-**Describe the bug**
+# Describe the bug
 A clear and concise description of what the bug is.
 
-**To Reproduce**
+# To reproduce
 Steps to reproduce the behavior:
 1. 
 2. 
 3. 
 4. 
 
-**Expected behavior**
+# Expected behavior
 A clear and concise description of what you expected to happen.
 
-**Logs**
+# Logs
 If applicable, add logs to help explain your problem.
 
-**Environment (please complete the following information):**
+# Environment
+<!--- Please complete the following information -->
 - HW: [e.g. SGX1, SGX2] 
 - OS: [e.g. Ubuntu18.04, CentOS8.1]
- - Occlum version [e.g. 0.16.0]
+- Occlum version: [e.g. 0.17.0]
 
-**Additional context**
+# Additional context
 Add any other context about the problem here.
 
-**Possible Solution/Implementation**
+# Possible solution/Implementation
 Not obligatory, but suggest a fix/reason for the bug.